Reddit user mfiasco posted an image of a note he left in his glove box that he claims resulted in the return of his car after it was stolen. Whether or not the car was actually stolen and returned is unknown, since the procedure would not have resulted in any actual police reports. However, the images of the letter and envelope certainly make them look like they spent time in a glove box or under a windshield wiper. And it would be nice to hear a story where leaving a nice note is more effective than leaving an absurdly mean one:

Sources: Reddit | Imgur