I lost my iphone and am trying to use MobileMe; what happens if a person restored it?

I lost my iPhone and am trying to use MobileMe to track it. Will I be able to find it even if someone who may have stolen it restored to factory settings?|||Lets hope that the person isn't smart or will return it. Did you have MobileMe before you lost your iPhone? Well go in and deactivated it and tell them to call you. Don't buy another iPhone yet. Wait for iPhone4