I suggest you also call the Police and check to see if it was reported lost/stolen. They may have a report and could connect you with the owner.

I found an unlocked diamondback bike on 2nd street in front of where I live on the night of 8/7. It was still there the next morning, still unlocked. I noticed some teens yelling expletives in front of the house where the bike was and I went outside, they quickly dropped the bike and ran away, presumably about to steal it. It's not a shiny new bike but it works fine and looks like it had been recently used. In any case, I have the bike and I would love to find the original owner!