Well, if its requested, it would no longer be on your shelf, the request removes it from your shelf.  But, aside from that, there has been a glitch in the system that has been causing this to happen it seems, its been a frequent post lately. Decline the request and in the area on why, put that you do not have the book and it showing on your shelf is a system error. You may also want to notify R&R via the Contact Us link at the bottom of the page.

This is some sort of glitch.  Not sure what is causing it, but it has happened to me twice and to several others as well.  I just canceled the requests and wrote to the librarian.  Carol Ann

Yes, this just recently occured to me as well.  In my case it was really freaky, because the titles were almost identical but two completely different ISBNs.  I had a book called Grace Notes by one author on my shelf, but Grace Notes Co by another author was requested.  At first I was wondering if I could have input it wrong, but the ISBNs are sooo very different, that wasn't possible!