Found someone else's ipone

Click here for information; in addition, post notices around where you found it, and if applicable, contact the Lost & Found department of the facility where you found it. Unless they left their contact information on it, or choose to approach you about it, you can't.

(210089)

That is only an option if the original owner has provided you with a message on the lock screen of their phone leaving a phone number. If they did not, there is no way to get a number. You can also try like a lot of people do and press and hold the power button to bring up Siri and say "Call Home". If it goes through to someone, ask about returning the lost phone.