I know you're joking, but for the sake of others...
And they would know this how? All they know is upon inspection, it appears that my phone wasn't abused, physically damaged, or dropped in water. They keep old DROID, I get new DROID, end of story.
CPUs do die of natural causes. Rare, but it happens. Besides, they wouldn't even investigate far enough to know if it was a fried CPU, or some other failure; i.e. motherboard, power supply, etc...