http://support.apple.com/kb/ph2701 If your device is lost or stolen, you can erase the personal information ( such as your contacts, email, and music) and settings on that device to prevent anyone else from seeing or using your information. Important: Before you erase all the information on your device, try to locate it or play a sound on it. After you erase the information on an iOS device, you won’t be able to use Find My iPhone to locate it or play a sound. You may still be able to use Find My iPhone to locate your Mac after you erase it. If you erase your iOS device and then find it, you can restore the information on the device using iCloud Backup (if backup was turned on before you erased it) or iTunes. For more information, see the user guide for your device in Safari bookmarks or on the Apple Support website.