Not my story, but one of a friend and neighbor.

Had his crappy newish low-end Raleigh commuter stolen. It was U-locked to a sign post. The thieves unbolted the post, and stole the bike with the lock on it.

After reporting it to the local police, the police actually made an effort to track down the bike and an investigator was assigned to the case. He scanned CL, and sure enough, there was the bike. It was advertised as needing to have the lock removed, since the owner had "lost the key". As a result, he was offering it "cheap".

The police investigator asked the real owner, my friend, for the key to the U-lock. He contacted the seller, and arranged to see the bike, bringing the key with him. When he saw the bike, he asked a bunch of questions, such as how long the seller had owned it (since new!). Then the police investigator tried the key, and it unlocked the lock. Cuffed the guy.

The bike was returned to its rightful owner, but the sad ending is that the seller had his day in court, and got off because it couldn't be proven that he was the one who had actually stolen the bike.