I have an itch collection, in the "add to wishlist" menu it supposedly has 42 items. When I actually open the page up and count it all I see 41 games. I can pinpoint exactly where that missing game used to be thanks to the collection viewer "skipping" a number when counting down. So the game's been delisted, I don't really care about that part, what I do care about is that the game is still on my list in a residual way. How do I find out what game that was, and how do I get that game out of my collection after that

The game was not delisted. If it were delisted, you would still see it in your collection.

It was removed from public access. Maybe deleted.

Some devs do this regularly.

https://itch.io/t/3693485/do-not-update-your-games-by-deleting-them-and-uploadin...

It also happens that games turn out to be malware. Or are removed by Itch for other reasons. But usually it was the dev that did it.

It is quite irritating either way. That we do not know which game, or why it is not available any longer.