It was a joke. ;)

This is yet another GOG bug, nothing more or less.

And I got the affected games "free with purchase" years ago. I also haven't got Daggerfall Unity - GOG Cut in my library (though I know that some of the people who also haven't claimed that have been affected by this glitch, so I doubt that there are any conclusions to be drawn from that).

My apologies - I could have known! :-)
But are these games really still in your library? It would mean that the games get removed selectively or time- or whatever-sequenced.

Yes, they've never left.
Again, the removal of these games from people's libraries is almost certainly a bug -- if there is any selectivity or order to it, it was most likely not of human intent. :)

Funny thing, I noticed that Arena and Daggerfall had been removed from my library. But only because at that same moment I found Daggerfall Unity in Daggerfall's place. I believe this could be related.

Today I just noticed that something was missing from my library. And, as above, the missing items were, of course, "TES: Arena" and "TES: Daggerfall," which I got free with the purchase of (I think) "Return to Castle Wolfenstein" (I'm also 99% sure that the fact that they were added to the library was also visible in the orders, but there's no sign of that now).

From the pages of the games in the store, with the purchase of which "TES: Arena" and "TES: Daggerfall" were added to the library free of charge, also disappeared information about it, e.g.
https://www.gog.com/pl/game/return_to_castle_wolfenstein
https://web.archive.org/web/20220422130316/https://www.gog.com/pl/game/return_to_castle_wolfenstein

Of course, they can be added to the library again for free, as they are now visible in the store as standalone items (which was not the case before when they were added for free to other games), but it would be appropriate for GOG to make such changes invisibly to the user, or at least inform them by email that due to changes in the store they are removing specific games from our library, but they can be added to it again for free.
After something like this, how can I trust that this will not happen in the future with other games, which I will only find out about when I myself (probably by accident) notice that something is missing from my library again?
Even if it were a simple bug (human or otherwise), I seriously should find out about something like this by complete coincidence?

To make it even funnier...
Some time ago I picked up "Oblivion" (as a key from Amazon). Currently, when I click on "View store page" in the game tab in the launcher, I am flipped to https://www.gog.com/en/games while when I am in the game tab (in the browser) I click on "Store Page & Reviews" I am taken to https://www.gog.com/pl/game/elder_scrolls_iv_oblivion_game_of_the_year_edition_deluxe_the where.... I can buy the game (again), even though I have it in my library and can install it normally (although something doesn't want to work for me, because only the game launcher starts, where I can, for example, set graphics options, then I click "Play" and.... nothing happens, "Oblivion" does not start):D
Despite the fact that I have "Oblivion" in my library, the store is convinced that I do not have it in my account (the same thing happens in the search results, where the "In library" designation appears next to the games I own - in the case of "Oblivion" something like this does not happen).

And so to conclude: it's a bit weak and unprofessional that for more than 3 weeks no one from GOG has deigned to answer the questions asked in this thread.

Same here, lost Arena and Daggerfall. Only noticed it by accident - there was a list of free items on the front page, and Daggerfall did not have a tag "in library."
The problem of not owned owned games is quite common. For me, the store shows both Fallouts as not owned but I have them in my library - bought before they were removed and readded. At least, this has a reasonable explanation. Trine 4, on the other hand, does not - the store does not show it as owned for me but it shows all DLCs as owned. Go figure.

There are 2 sets of Fallout games. You problably aquired them before Bethesda bought the rights. Then they were removed from the store and later rereleased as Bethesda version.

Arena / Daggerfalll and Fallout (1,2 Tactics) are not comparable. Fallout was never removed from customers' accounts, while Arena and Daggerfall were (and had to be reclaimed). Moreover, I remember that GOG communicated that the Fallout games couldn't be purchased anymore, but would remain in customers' accounts.
The other difference is that the old Fallout games (now suffixed "Classic") can't be obtained (with or without payment) for anyone - you can purchase the new Fallout games only (I don't know what the maintence situation is - I don'r think the "classic" Fallout games will ever see an update, while the new ones may be updated if necessary). On the other hand, Arena and Daggerfall can be obtained for free by everyone.

With that said, the way GOG treated the status change of Arena and Daggerfall (from free bonus to generally free games) was, mildly worded, not a good example of customer focus and great communication processes - possibly caused by human mistake (but why not explain and apologise?).

I don't have them, but I think I remember reading that the "classic" builds got updated to match the new ones (basically just replacing mentions of Interplay with mentions of Bethesda) some time after Bethesda returned them to sale here. At any rate, I think the only significant difference is still the extras.

Thanks for the information.

According to gogdb.org, here are the properties of the english offline installers for Windows:

- Fallout Classic, Version: 1.2, Date: 2015-08-26, Size: 526.4 MB
- Fallout, Version: 1.2, Date: 2019-02-04, Size: 720.4 MB

- Fallout 2 Classic, Version: 1.02, Date: 2015-08-26, Size: 756.0 MB
- Fallout 2, Version: 1.02, Date: 2015-08-26, Size: 756.0 MB

- Fallout Tactics Classic, Version: 1.27, Date: 2015-08-26, Size: 1.8 GB
- Fallout Tactics, Version: 1.27, Date: 2015-08-26, Size: 1.8 GB

Data are similar for other languages installers.
Basically there seems to be a difference in the two releases of the first game: I'm not sure about the what this difference consists in because, as far as I know, no official changelog was shared.
I'm not considering the differences in bonus contents,

Just chiming in to say I just noticed this when I saw I didn't "own" them on the store page. I know I had them in my library prior to this, as I've long since downloaded and stored them away, so that's both somewhat disconcerting and annoying, personally. There's an expectation that games in our libraries are permanent, even if they, realistically, aren't.

Wouldn't want to someday find games I paid for missing, that's for sure.

A very valid point. It happened to me once a couple of years ago that two or three games (of the same publisher) disappeared from my account at a game download portal (not GOG, and not Steam), when the business relationships between the publisher and the portal ended. The portal didn't inform me (otherwise I could have downloaded these games before they disappeared), and said they had no choice, for legal reasons, when I found out and complained. Well, they never got any money from me after this has happened.

I'm not sure what the legal situation really is, but I suppose we customers are in a weak position - and be it only because of the high costs, risks and time it takes to get a final court decision and real payments if you succeed at court, possibly in a foreign country, too. On the other hand, portals like GOG or Steam would probably think twice before they removed paid content from customers' accounts, because of the revenue and market image consequences (assuming a considerable number of customers would mind such an action and react accordingly with more than furiously shouting). And there is the (probably small) risk that they go out of business without a successor taking over the accounts (Desura, for example - but even they gave their customers a warning and time to download their games).
And who could or would download all games of their GOG or Steam accounts, just to be protected against the removal of games?

The 26th of August, 2015 seems to match up with when Bethesda returned the old Fallouts to GOG, so that seems to support what I heard about the "classic" versions being updated to match the new releases at that time. Not sure what the size discrepancy between the old and new versions of the first game is about, but the fact that version numbers between are identical leads me to believe it's probably Galaxy-related feature updates or additional compatibility fixes or something.
Edit before posting: Got curious, and with a bit of looking, this is the first relevant bit of info I found: Now I guess we can all get back to developing theories about why the Lizardmen directed GOG to remove Arena & Daggerfall from most people's libraries, but spare other people's copies. ;P