I have had a similar thing happen a few times.
Chances are if the has gone for below the reserve then the reserve is set to high!
If I were you I would send an quick email asking if he still interested in selling for the price you won at?
Thats not strictly against the regulations of ebay, as long as he puts you as the winner and you pay through ebay/paypal or he re-lists and you buy it now!
Hope that helps
PM