My first BRAND NEW car was a '76 Camaro. I cherished this vehicle, as my family wasn't much in a position to buy new cars all that often. I attended a function with valet parking and lo and behold, the car came around the bend with a horrible knock! Sounded as if the lower end would let go any minute. The car was immediately shut down, left on the property overnight. (great evidence) The next day it was towed away (more evidence) and brought to the selling dealer. Apparently what the irresponsible youth had accomplished was drive some carbon down a cylinder wall, throw a belt, and bend a pully. The car was repaired,(they ran a cleaner through it) fixed the pully and belt. Even though it could have been a lot worse,The valet service refused to admit guilt and make good on my expenses ,caused by their service. Since the damages were less than $1500 (remember this is 30 yrs ago) , I sued in small claims court (with out a lawyer). I presented my evidence, tow receipts, repair bills, etc. The judge ruled in my favor, forcing the service to pay. So, a couple of things here, first, the "walk around", before you release the keys, lets them know you are looking (you may nicely ask the attendant if he wants to take a look ), second, I usually take my '98 Crown Vic, third, you probably will have to sue because the service will not roll over (if you decide to persue this). Finally, if you present a good case to the judge, you'll have a good shot at coming out on top. At the very least, you will get their attention, and force them into court spending time and money.
PS, or, you can do like Kevan, nobody drives your vehicle but you.