Look, there are some people out there who wouldn't bother returning your lost phone, and the best you can do is try to appeal to their conscience. One way to do that is through Android Device Manager, which now has the capability to add a callback number on the phone's lock screen that the finder can contact. You can now even write a message to the phone's finder (or thief, if you're unlucky) on the screen through the "lock" section of the app or web menu. The Device Manager, for those who've only just heard of it, is an app that lets you find lost devices remotely, or lets you lock them with a different pin than the one you typically use through its web interface. These features give the person who picks up your phone a really easy way to get in touch, so make sure to update the app, just in case you end up needing them.