Time for a beer

.... so if this is true why dont they also know where these cars are?

Who said they don't.Only 2 left for the dealers.The rest were picked up in production.You could say it was "human error".

These engines are ran and hot tested before they are shipped,but when your bench testing an engine with a larger cooling system volume than the actual vehicle's cooling system they simply dont overheat during testing.I think the most impressive thing is that the machining is so precise that they can run without a headgasket and not leak.I've seen them leaking with a gasket.

.... hang up the phone and pull the head apart

You dont need to remove the cylinder head to prove the gasket's not there.Just have a look directly below the thermostat housing where the head meets the block and you should see a metal tang hanging out.