Game removed from library?

Free games also count. Maybe you deleted one?

https://store.steampowered.com/account/

• check also this list.

Have you uninstalled any free games? Those typically don't count towards your game count once you uninstall. Your notification would probably be your only conclusive way if it wasn't a free title. You can check your redemption history in your steam settings (click your name in the upper right corner and click "account details") but I doubt a removal would be there.

Ending my statements with a question mark?

Your profile says you have 779 games, so maybe you mean your in-client library? Maybe you've hidden it or put it in some category by accident, if that's the case...

Evil maze or something from gleam? Or maybe free beta?

I think It was some beta or alpha game. Some beta keys can expiried without info about end of test.

It probably was bloatware anyways...