I'd have to agree that it shouldn't have overheated that bad that quickly. Unless he sat there without the car moving just idling for 15-20 minutes on a very hot day (90+) I don't see why it would overheat that quickly. The fuse isn't supposed to blow, the fact that it did is a red flag. Fuses blow when there is too much current, that means there was an issue. I'd demand more of a result than just replacing a fuse.