I just bought a Trek and registered it with Trek, using the serial #. Perhaps if you contact Trek, explain the situation, and include the serial # of the bike, they might contact the owner for you, assuming the owner bothered to register it. That seems to be your best bet.
If that doesn't work and the police still don't have a theft report on it (strange), the only other thing I can think of is to post a short notice in the local paper, or one sign somewhere in the area, that you found an abandoned bike, but don't describe the bike at all so you can verify that it is indeed the owner trying to claim it. That seems iffy but would be worth a try. Then I'd say you've tried your best.
Last edited by goagain; 08-07-11 at 09:37 AM.