What to do if your iPhone is lost or stolen
Step 1. Set up an AutoLock passcode
AutoLock is one of the iPhone's most basic security features. When you set a passcode with AutoLock, the phone's touch screen will automatically lock after it has not been used for a certain period of time. You have the option of having your iPhone's screen lock after either 1, 3, 4, or 5 minutes of inactivity.
You also have the option of completely disabling AutoLock if you ever desire to do so. By default, the feature is turned on. However, you can always turn it off by simply opening iPhone Settings, opening the General tab, and selecting AutoLock. On the screen that appears, you can either turn the feature off or set the time period you want to pass before your iPhone locks. Once you have selected your desired settings, tap the box in the top-left corner to exit the AutoLock and Settings sections.
On its own, the AutoLock feature is not really an effective security function. However, it becomes a critical security feature when it is combined with the Passcode safeguard described later.