If your iPhone gets misplaced or gets stolen by someone, you should immediately use ‘mark as lost’ option in the Find My application. This feature is available for iPhone, iPad, iPod touch. When you mark as lost, it will lock your screen with a passcode. It lets you display a custom message with your phone number in order to get it back. You can choose to remotely erase your device if required. Your custom message will continue to display even after the device is clear.
The activation lock works in the background making it even difficult for somebody to make use of or sell your stolen or missing device. At the same time, lost mode clearly gives an indication to anyone who finds your device, that it still belongs to you and cannot be reactivated without your password.