Have you tried opening a support ticket? I have over 1000 games and this hasn't happened to me.
If your ticket goes unanswered for days (after the weekend), you can try pinging Firek about it.

Damn, I knew this would be something serious. Not only does the title have a full stop, but it has a space before it!

Honestly, looking at the thread all the useful things have been said already. Hopefully GOG staff will pick up on this soon, but it is the weekend so I wouldn't necessarily expect anything until monday.

You should have an email receipt for each game that was purchased or added to your account through one of GOG's giveaways. If the account refresh does nothing then open a support ticket with copies of your receipts and they can add them back into your account.

You purchased here and you should have receipts and no worries as it's probably a bug/glitch and it will be sorted.

Are you absolutely sure you only have one account?

^ I'd double check that account name too. jt2755 vs jt2755m = same 2 letters before the same 4 numbers plus that other account has the same "over 1000hrs on Witcher 3" you claim is missing. If you can remember buying any other games from GOG other than Witcher 3 and they're on that other profile, then it's entirely possible you have two accounts but simply logged into the wrong one.

You login to your GOG account with a certain email address, right?

Go check your old emails in that same email account, do you have receipts from GOG for your purchased games? They are your primary proof of purchase.

If you don't see such receipts at all, then I am 99% sure you have created several GOG accounts, and you just happened to log into the wrong account. I have no idea why someone would create several GOG accounts though; in one similar case someone claimed he had accidentally logged into his wife's GOG account, and hence didn't see the games he was expecting to see in the account.

Either that, or he was cross-sharing GOG accounts with his friends, and just forgot that certain game was on his friend's account, and not his own. Which in itself is forbidden of course, the games you buy to your account are only for your personal use, and maybe your household/family. You are not supposed to share your account/games with your friends.

Not saying that this is the case in your case, just as a reminder to everyone who is confused what DRM-free means. No, it doesn't mean you own the copyright to the games you've purchased, you bought a license to use the games.

I think this confirms it:
https://www.gog.com/forum/the_witcher_3_wild_hunt/cannot_save_or_delete_please_help/post8
;P

I knew I smelled fish.

lol

Another case of "GOG is the worst because I am a moron! Don't buy here!" never to be seen again?

You see, you're missing all the exciting stuff when you're not here!