How to find my lost iPhone 4s?

I recently upgraded to an iPhone 5 so I gave the 4s to my son. The phone doesn't have cell service so I can't try to call it. I've tried Find My iPhone but it's not listed as one of my devices, and honestly, I don't think I had ever turned that function on. I think he left it at the restaurant we ate dinner at last night but when I called they said they didn't have it. Any suggestions?

If you know your Sheriff go to him. They have a way of finding a phone. They are trained with Forensics in phones and they have ways of finding the company. Also, sometimes your carrier can help you out but a cop should be able to find that phone, providing the GPS is inabled.

Your screwed. Plus iphones suck

My only suggestion would to keep looking for it. Without cell service police can't track a phone unless they have high tech tracking devices, but you would still need the model or serial number. Your best bet is to report it stolen to your carrier with the cell phones serial or model number if you have it, this would alert the company if anyone tries to activate it that it is stolen and they can contact you. There really is no other way of finding it:/