i had a similar thing a few years ago after my car had been in a prang. The bodyshop (vauxhall my insurer insisted on despite it being a toyota car) managed to create a dent in the drivers door as if someone had opened it onto a post.
I complained and the guy said exactly the same thing yours did : "if it was one of our guys they would have said, the only guy who had access to it was the resprayer hes not in but ill ask" 2 days latter a call "yeah, my guy says he didnt do it". Its funny that dealers have this confidence in their workers, as if every mechanic and dealer worker in the world has the morales of a saint.
So i know where you coming from, they never took the blame for that one, sold it with the dent.