Seriously, don't give up on getting it back just because you don't have the frame number. I got my Inbred recovered by the police (the actually went and found it once they knew it was worth real money), and I didn't have a frame number. I did, however, have my knowledge of the bike, so I could tell them what forks it had, down to exact model and year, exactly what parts were on it, where there were little dings etc.
Alternately, be the winning bidder, turn up mob handed and take it off him. The guy blatantly knows he's shifting stolen gear, which is why he's got a fairly new account with 1 feedback.