I had a strange situation about a year ago. I won a fairly worthless CGC graded book in an on-line auction held by a very well known comic book retailer. When I went to register the book, it came back as still being owned by someone else. I tried to register it multiple times, but had no luck. After the third or fourth time, I contacted the registry folks about it, and was told the previous owner was refusing to transfer the book because it was "stolen." I had repeated emails with the CGC registry person, and after explaining where I got the book, he asked me to send him proof of my winning the book in an auction. I sent screenshots of my account from the on-line retailer showing the book in my list of purchased items, as well as screenshots of the book in the auction listing, all of which included the registry number. After providing this information, and spending what amounted to hours of my time dealing with a book I won for less than $20, the CGC person never responded, and I have been unable to add this book to my set to this day.
Now, I'm guessing that the previous owner was possibly miffed that their book sold at auction for less than it cost them to grade it, but, after dealing with a CGC representative, providing all the proof I was asked for, all irrefutable by the way, I fail to understand how this company could simply stop dealing with the issue and fail to resolve it.
So, be aware everyone, apparently if you sell a CGC graded book you own, don't like the price you got for it, you can enact your revenge by refusing to transfer ownership and accuse the new owner of "stealing" the book and CGC will simply go with it. I can only assume the CGC rep decided that this worthless book wasn't worth his time either. Good thing under $20 isn't worth the time of law enforcement either, or I could be looking at some serious hard time for this. Or not. Well, no, not even remotely.
Makes a good story for my friends who think "professional" grading is a fiasco on multiple levels though.