Where does sneaky damage happen most often?
Number 1: Under the front air dam.
Many modern cars are low, like this one above.
If a valet service is parking your car in an old garage or old lot where the concrete parking bumpers and curbs are high, there is a real chance the bottom of your air dam is going to be scraped, cracked, or worse.
Two or three decades ago it didn't matter so much if curbs and parking bumpers were a little high, because cars were higher. But now those high-curb garages and high parking bumpers are an on-going problem.
You can't count on valets not to grind your air dam. There are valet services that are scraping air dams all day long, every day... because they're idiots.
If you ask a valet how high the curbs are in their garage, or how high the parking bumpers are, I doubt they will know the answer... because the training they get is not that thorough, and it would be rare for a valet worker to take initiative to know this answer.
Low car owners, offering a twenty to keep it up front is sometimes the better, safer, cheaper way to park.
Number 2: On the rims.
Rims get scraped frequently.
One telltale sign that your rim just got grinded along a curb is seeing white powdery dust on the sidewall of a tire... unless the valet has already brushed the dust grindings off.
You should document the condition of your car immediately before handing over the keys to a valet by using video. Get video of each rim. Get video of the underside of the air dam and each corner of your car.
And when your car is returned to you, run your fingertips under the air dam. If there are now areas of the air dam that are rough to the touch, then yes... a valet probably drove it into a curb.
Look at and study each rim. Check the edges of each rim thoroughly.
Number 3: Dings on the body.
In a typical valet parking operation, most of the parking spaces are TIGHT. They are all about efficiency and squeezing the maximum revenue out of the parking facilities they control. First and foremost they care about money.
In the photo above, those wide spaces would be considered wasteful. If this was a valet lot, the valet company would likely have this lot re-striped so they could fit in a lot more cars.
The matter of customer-cars-more-frequently-getting-dinged is barely a consideration at all.
If you see any chubby valets working where you are about to park, this could be especially bad for your car. Chubby valets are not able to squeeze into parked cars as easily. It is more likely they will ding a lot of cars when opening car doors.
Another matter of concern is if a valet is using a public lot or public garage. With public parking there is a lot less control over the welfare of customer cars. Non-valets are probably more likely to ding the car next to them. And they are more likely to park so close to a neighboring car that a valet will need to attempt entry through the passenger door.
Unless you are making a special arrangement with a valet service, don't expect that your car will be placed in a nice wide space. It probably will be tight. So look over the sides of your car very well for new dings and scrapes caused by car doors hitting it.
Number 4: Damage on the corners.
Valets sometimes kiss the wall when maneuvering a car into a parking space... because they screwed-up in judging the distance. (I'm thinking of the Maserati GranTourismo. Their front-ends are deceptively long.)
Sometimes they back into other cars or objects.
Sometimes they leave it in drive after shutting it off, and the car rolls a foot or two into the wall.
Sometimes they leave it in neutral without the parking brake on and it rolls.
So the four corners of your car are another area that should have your attention when your car is returned to you.
Standard procedure upon your car being presented to you by a valet service should be to do an immediate and complete vehicle damage analysis, before you hand over the departure tip.
They might seem like really nice guys. They might strike you as being complete professionals. But you still must verify they did the job right, BEFORE YOU DRIVE AWAY.