Thats the thing though, I do still see a couple games that were removed by itch in my collection, but the game I'm looking for is just gone.
Grats on finding it.
There might be several stages of removal, when Itch does it, so they can rollback or whatever. But if it is fully removed (or made unavailable), that looks the same. Hole in collection.
My best guess is, that in this case the dev made the game un-public, since the account seems to be still there.