Confused: Will Find My Mac work if the thief just did the hold ctrl and power button restore?

Recently had my macbook pro stolen. It's a mid 2012 model with mountain lion so it can reset the OS by just by holding ctrl and the power button. I've done it many times myself so I know all they have to do is go erase the Mac HD and then reinstall OS.

I tried to use Find My Mac and it still says offline. It's been almost two weeks. I know there's a chance the thief just may not have turned it on yet but if all they did was erase my HD and reinstall OS, will Find My Mac stop working? I don't want to waste anymore time hoping to get it back if it's that easy to do so. Please help me out!

Someone please help..idk what to do. I've read on other questions that I still may have a chance, how?

It wouldn't hurt to report it stolen to your local police and to Apple, especially if you have the serial number. If you don't have the serial number but you have the purchase details, your dealer may be able to recover the serial number.

From apple.com/au/contact:

If you have lost or found an Apple product, contact your local law-enforcement agency to report it. You can also find a list of serial numbers associated with your Apple ID and get information about using Find My iPhone for iPhone, iPad, iPod touch or Mac.

Software running on the machine (About This Mac, System Information) can look at the serial number. It is hard (but not impossible) to wipe the serial number from the machine.

I wonder what happens if the thief (or reciever of stolen goods) sets up the machine and Find My Mac. Does Apple use the serial number, or just the user's Apple ID?