Blown engine possibly

I had to replace the timing cover, well when I put it all back together it sounded like it was out of time. Well, I drove it like that for about two weeks then one morning I started my car and it was idling and all of a sudden it shut off and never started again. The dealership says the engine is blown. It sounds as if something in the top end is not turning with the, whole engine. Could it have bent a valve? Or what is wrong?