There are apps for most smartphones that allow you to find the phone’s location via GPS or cell tower triangulation. I’ve read stories about people using this to track down stolen phones, where they confront the thief, who then sheepishly returns the phone. (Side note: confronting thieves is not necessarily a wise idea, as you never know how they’ll react.)
But the system isn’t perfect. For some reason, certain Sprint phones are erroneously reported as being located at a man’s house in Las Vegas. For the last couple years, Wayne Dobson has been accosted by irate phone owners and police, at all times of the day and night. He’s even put up a sign saying “NO LOST CELL PHONES!!”. But recently the encounters are getting more serious, so Mr. Dobson has publicized the situation. Hopefully this will prompt Sprint to fix the problem.
Note that this isn’t the first time Sprint has had this issue.