I've been racing R/C cars for a loooong time and I've NEVER seen a rod break through the case. The only possible way that would ever happen is to lift the car off the ground and hold it wide open until the rod broke, but even then it's VERY unlikely..
A rod will not break unless the engine has been at unncessarily high RPM's for any length of time. If you never did anything like that to it, it's his fault.
Sounds like misuse to me.
Aaron Waldron - LiveRC