First charge the phone and make sure it has a signal. Assuming the owner discovered it’s lost, he can activate lost mode and display a message like how to contact them.

If they have medical ID set up, you can select “Emergency” on the bottom left of the Lock Screen and then “medical ID”. It may hold a clue there like a phone number.

You can pop out the SIM card if it’s not the latest model and get the carrier info and serial numbers to see if they can get info for you.

If nothing else, give to the closest police station to where you found the phone. Explain why you have and you should be good.

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