Losing your phone can be a nightmare, but if it's an Android phone, you might be able to recover it with Android Device Manager. You can lock your phone through the browser-based Android Device Manager, after which you can choose to set a "Recovery Message" which is a message addressed to the person who finds your phone. What you write is totally up to you; you can appeal to their conscience, offer a reward or threaten to hunt them down. You can then enter an unlock password and your contact number. The rest of your phone's functions and data are locked, so the password only lets the person call you. The feature is built into phones running Android 4.4, but you can download the free app if your phone happens to be running an older version of Android.