Well, Adobe withdrew my support ticket for this problem without even attempting to help. Digital Editions is now telling me that there are too many activations for my username. If the software worked properly in the first place this wouldn't have even happened.
So at this point it doesn't look like I will get my books back at all.
You now have two accounts with two books linked to two different accounts. I suggest asking the vendor from whom you bought the first (anonymous) book to re-issue it to you one more time. As for the number of activations, Adobe customer support should be able to resolve that.
Did you get this fixed? I have the same problem but with over 100 ebooks. The vendor states the download is already registered to another user (namely the 'unauthorised' one). I currently have a web case open but Adobe posting a fix would be useful since I can see this problem has been going on for years...