An Android device has a built-in feature that will allow you to add a lock screen message to your phone. In this message, you can write your contact info and a good number to call to notify you when found.
It is important to note that some of these steps are newer features of Android Oreo.
To add a lock screen message go to your devices Settings App, then tap Security & Location. Next to “Screen Lock” tap Settings, and finally tap Lock screen message.
From there you can add your personal contact information so that if found, that device will reach you much quicker.
Try not to put too much information on the lock screen, because anyone can view that information without putting in your device's passcode. “If found reach me at…” should be followed by an email address or a number of someone close to you.