Find my phone

This document has a list of things to do if your iPhone, iPad, or iPod touch is lost or stolen. --> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

- The Find My service described in the article is the only recovery feature Apple offers. It must be set up before the device is lost.

Read this document for how to use the Find My app to locate a missing device or item --> Use the Find My app to locate a missing device or item - Apple Support

The chances of locating a device depend upon which features you selected in:

Set up Find My on your iPhone, Mac, and other devices - Set up Find My on your iPhone, iPad, iPod touch, or Mac - Apple Support