In that case there is not much you can do. There is a chance someone may try to return it, but it's not like we have the ability to turn your phone on remotely and GPS locate it
If it were my phone, I would just deactivate the service and get a replacement. Since it's not a smart phone, it shouldnt be too big of a deal.
Just follow up to see if anyone returns your phone over the next few days... Someone has to find it.