Sure. But if one didn't care about a game for five years, why would he now?

Another delisting I missed. Make thread sticky is perfect way how to hide it:)
What about send "delisting" message to everyone? Similarly like messages about wishlisted games on sale?

I have numerous games on my wishlist that I care about, but I have to prioritize based on time, cost, size of backlog and dwindling hdd space. Sometimes I'll forget about something I wanted as it gets buried in my large wishlist, sometimes I'll only bite the bullet if i've budgeted enough and a good enough discount happens at the right time (or in some cases, refuse to buy a game on principle until it is given a discount at all, looking at you Terminator: Resistance). Granted, 5 years is a long time, but there are plenty of reasons for someone to put off buying a game they might still want.

so true!

Given that during these years it was available for less than 2€, it must have had a very low priority indeed.

I too missed games on GOG and it also bothered me for a moment (one came back: the original XIII)
But in hindsight I know that I could have just bought them if I really wanted them.

How is having a sticky at the top a perfect way to hide it?

Because of direct jump over sticky threads to "regular" ones:)

Are you doing that manually?

Manually? My eyes immediately jump to first non-sticky thread.

Stickies are at the top for me.

Raiden IV was removed some time back, and now Raiden III. For the games I own, I created a tag called "REMOVED FROM STORE" to tag them. Once and a while I check to see - some things have come back as-is, some have returned with a different/better/upgraded version (I still have the old version, no automatic upgrade or steep discount for previous version owners), and others are still gone from the store (but I still have it in my library).

Once a game is no longer in the store, do most folks keep a download copy of the installs and goodies, just in case they are forced to remove all remnants? Had anyone ever seen a game removed from their library without notice/refund?

As fas as I know, the copy you own is yours to keep. They have never removed any delisted games from my library. In short, I still have access to the offline installers. I dont use Galaxy, so cant speak for that.
.
Edit:
I just checked Grandia II AE and I still have the option for offline installer.
.

Timberborn demo
https://www.gog.com/forum/timberborn/demo_delisted_and_removed

I completely understand removing demos - especially if no-one actually paid for them (I think I have seen one before on here that was free, was a demo). Glad to see that nobody quickly comes up with examples of paid-for games that were delisted and removed from accounts.

When a game is delisted and a new "enhanced" version replaces it, it would be nice to get a previous-version-owner discount or something...