If you can’t find your device, use Lost Mode right away to lock it with a passcode, display a custom message on the screen, and keep track of its location. You can simply turn on the lost mode via the Find My iPhone app or at www.icloud.com/#find
If you put your iPhone 6 or iPhone 6 Plus in Lost Mode and you have credit and debit cards in Passbook for Apple Pay, Find My iPhone attempts to suspend your cards immediately, even if your iPhone is offline. To resume using your suspended credit and debit cards, you will have to turn off Lost Mode, then sign back in to iCloud.
Lost Mode requires an iOS device that meets minimum system requirements. You can lock a Mac or iOS 5 device, but you can’t track it. When your device is in Lost Mode, it doesn’t display alerts or make noise when you receive phone calls, messages, or notifications, or if any alarms go off.
If your device is online when you put it in Lost Mode or lock it, it locks and tracking begins (if applicable). If Location Services is turned off on the device, it’s temporarily turned on to track your device’s location. A confirmation email is sent to your Apple ID email address.
If your device is offline, the passcode lock and tracking (if applicable) take effect the next time it’s online.
You can turn off Lost Mode by entering the passcode on the device, or by clicking on STOP LOST MODE when signed in to www.icloud.com/#find