I think you should, but you should definetly be prepared to hear this guy yell at you about how you're snooping around in his stuff. As for putting in a T-Mobile phone, I'm not I don't think you can. SInce the Sim Card says At&t on it, I doubt you can.
well its defiantly not an iPod if it has a sim card what you found is most likely an iPhone and they dont store contacts on the sim card like normal phones try taking it to a lost and found near the place where you found it
You can't stick a T-mobile sim card in it because the iPhone and any sim card other than ATT won't work. So I don't know!
This may sound horrible, but if you can't find the gu within 90 days, it is legally yours and you can keep it.