Sadly the item doesn't show on that URL, or under 'My Collections' on the browser; I only see it in the desktop app, at 'itch://collections/'. I'm pretty sure this is a programming bug where that view is showing an item that's been deleted from itch.io, and I can't find any option to remove it from the collection.
Again this is a really minor thing and doesn't break anything! But it bugs me a little :^) if it doesn't get fixed I suppose I can delete the collection and make a new one without this game.