If you have the Find My iPhone and Find My Mac apps enabled, you can take steps to find your lost or stolen iPhone, iPad, iPod touch, Apple Watch, or Mac. Using the Find My apps allows you to put your missing device in Lost Mode, see its location, or erase its data. Other than the Find My iPhone and Find My Mac apps, there's no other Apple service that finds, tracks, or flags your device for you. Learn more about Find My iPhone.
If you have AppleCare+ with Theft and Loss, you can start a claim for a replacement device.
Your Apple product might be covered under your wireless carrier plan. Make sure that you report your lost or stolen device to your carrier so they can disable your account to prevent calls, texts, and data use. Also, make sure to contact your local law enforcement agency to report a lost or stolen Apple device.
Learn how to locate Apple product serial numbers.