Call the nearest Apple store. Tell them you are mailing in a lost phone and need their address. Wrap some cardboard around it, stick it in a bubble-wrapped envelope and send it along with your contact info.
For 3 bucks or less it's the right thing to do and maybe you'll get a reward or at least the postage back from the owner.
For 3 bucks or less it's the right thing to do and maybe you'll get a reward or at least the postage back from the owner.