[Wisconsin_Snake]

Did they say they were going sandblast them???
If there was pitting, that would show through, not sandblasting them and just coating them would show through too, but that would probably would give you a crinkled appearance. Beside looking crappy, I would be concerned about the rust that was left on further rusting the metal and not providing a good surface for the jetcoat to bond with..
Post a couple of pics so we can determine what happened.