There were 99 games in my wishlist. One game gone a couple of hours ago.

I don't see any fresh "removed from the store" topics and can't hold all these wishlisted games in my head to say which one of them is missing.

Maybe you had Thronebreaker (Gwent's DLC, not the new one) on your wishlist?

I know that some new games disappear from wishlist after release. But the only game in my wishlist that is still unreleased is System Shock remake. Others are pretty old games.

Update: Sorry, I missed an explanation in brackets. Anyway neither new one Thronebreaker nor Gwent's DLC never were in my wishlist.

So it could be Deus Ex GOTY.
According to GOG Database It was delisted today for a short time.

Maybe it was "The Walking Dead: The Final Season" which was removed a few hours ago from sale because Telltale probably won't finish the game before closing up shop.

Deus Ex GOTY is already in my library.

Maybe something else was delisted and quickly returned today? Like I said: pretty old games only.