as an attorney who doesn't do much in the PI business, this has usually gotten their attention.
Just ask them to bring you another one.
Same miles, same history, same condition. And get it here now.
Just let them know that all you want to do is to get back to where you were before their idiot made all this mess. They were on notice that he was a risky driver, as this was obviously not his first problem. Don't be an ass. Just very calmly tell them that the easist thing to do would just be to bring you another car. Just like the one you had.
Patience. This ain't going to get taken care of overnight.