If you return it to a cell phone store(I'm assuming it's a sprint phone), They should be able to take the battery out and look up the owner by the ESN/IMEI under the battery. Hope this helps

Turn the telephone in. It belongs to someone. Preferably - turn it in to the service provider who is at least in a position to return it to the person who lost it. If this WERE your phone, would you expect any less?

Then, you should file a police report outlining what you did so if the person calls the police in your area, the police have some idea where the phone is. Would you expect anything less.

Why keep it anyway, you cant work it.

Thanks in advance for being honest.