I can only assume the dev deleted it since ones that itch took down are still in my library. The game was uploaded a few years ago and I think it was a year or two since it was last updated. Really wish I could remember more about it.
That looks the same. You can't tell who removed it. Only that there is a hole in your collection. Took me a while to figure out that most of those are developers that delete their game and make a new page with the same game. But if it was not updated for long, that sounds like some other reason for removal. Though I also saw devs that would remove a prototype and upload a new project with the finished game.
Oh and yeah, I saw malware on Itch that lived for two years. And stolen games for over half a year. https://itch.io/t/3512426/itch-is-not-a-safe-place-do-not-download-things
If you remember last time you visited the page and your browser's history from that time still exists, maybe you can look there for clues.
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.