When I was registering a book, my computer hiccuped and logged me out while I was trying to do so. So I logged back in and registered the book. I went to see, just incase, there wasn't an incorrect copy listed.
I've seen that happen a time or two, though not often. Since the book shows as registered by AnonymousFinder and isn't connected to your bookshelf at all, you wouldn't be able to edit the book details even if you had the full BCID, though you could make a journal entry and keep track of it that way.
I'd say ignore it - though support could delete it entirely.