What should you do if you find a bike that appears to be stolen? What should you do if you find a bike that appears to be stolen? Should you turn it in or just leave it alone? Occasionally I'll see a bike that appears to be abandoned, which I assume to be stolen for a joyride then tossed. It's possible that the true owner just left it by the side of the road, but it's also possible that it was stolen and by reporting it to the police I can help the owner recover it.

This morning on my ride to work I saw a pretty nice looking cruiser tossed in the ditch. I decided to call the sheriff and the dispatcher who answered the phone basically said "What do you want me to do about it?" She said she'd send a deputy to pick it up, but pointed out that if the owner left if there, it would be gone when they came back. Based on the location and time of day, I really doubt the owner left it there. Still, she made me feel pretty dumb for just calling it in.

My thought is, what's the probability that the bike actually was stolen AND the owner reports it stolen and gets it back, vs. the probability that the owner just abandoned it in a weird place? Is it likely enough to be returned to the owner that it's worth turning it in, or am I just wasting everyone's time? 

If my bike was stolen I would report it, but that doesn't mean everyone will. Also, if a bike was unlocked outside a business, or in someone's yard, I wouldn't assume that it's stolen. I'm talking about finding a nice bike ditched in a poorly lit area that's inconvenient to walk to, in a high-crime part of town.
As private citizen you cannot do much more than reporting it to the police.

If it was stolen and the theft reported, the legitimate owner may have it back.

If it was thrown away, there is the chance that the police will arrange the removal.

(Both points strongly depends on the country where you are located. In some places police officers may simply laugh back at you for reporting a suspected stolen bike, but again, if you take it you are breaking the law, too)