Something similar happened to me When I bought a board off here. Same situation with the authorities, the police couldn't even decide if it should be my local lot or the ones up near the con man who should take jurisiction.
I googled his email address and found his myspace account, so I messaged him & his mates on there. I was getting somewhere until he realised who I was and blocked me. then I did a search on all his posts on here, made a list of the top ten people that he seemed to know and chat with, then messaged all of them. One of those turned out to be a local mate of his who said the guy was being a flake and hadn't sent it. The mate kicked his arse and finally got it posted.
It is possible, but to be fair I was lucky that the guy I had a problem with was just a jerk, not an actual tea leaf. This is how to stalk a crim.
How to catch an iPhone thief: Busting an iPhone thief