Antique, so sorry that happened to you. I had something similar happen a few months ago.
This person won an item, paid with Paypal, and it needed to clear first. Once it cleared, I sent. Within days he negged me and said he wanted his money back (in the feedback). I thought, uh oh, I've got a scammer on my hands as there wasn't enough time for the item to get to him. Anyhow, long story short, he immediately filed for refund with Paypal which I was forced into doing (for the reasons you outlined). I was fuming. It wasn't nearly as much money as you lost, but it was enough to bug me because not only was I out the money, this idiot ruined my feedback. Up to that point it had been perfect. Then a coupe of days later, some other fool gave me a negative but that's a whole other story.
Anyway, I decided to not take it lying down. I wrote him an email and outlined to him that I knew he got the item, and that I had filed with the USPS fraud dept. and that I was in contact with his local Postmaster (you can get the information on the USPS site).
I further told him that I was getting in touch with his local police dept. AND his local district attorney's office. I was very specific in that I looked up their address in his town so he knew I wasn't bluffing (or at least it lent credence to what I was suggesting).
Lo and behold, he suddenly admitted he got the item. It still took me quite a while after that to finally pay me and only after a few more "threats" from me.
This guy is now naru'd due to a bit of shill bidding. How do I know why he was naru'd? Well, let's just say that even after I got paid by this con artist, I made it my mission to keep an eye on his ebay activity, and suffice it to say, he is no longer an active member (at least not with the two id's he was using).
Do a bit of leg work Antique. Find out the address's and phone #'s and maybe even the names of the local authorities in his home town (hopefully it's a fairly small town) and you might be surprised how he will suddenly find his books. See, it is possible that his mailman may remember delivering your parcel. It's worth a try. GOOD LUCK!!