Or nothing. Without more evidence, it's still he said she said and since it's their garage, they can do whatever they can to clean up before the cops get there. And, let's face it, since cops are there to keep the peace, they will do it in the most convenient way possible... and that may include doing nothing. At least, that's how they work in New York.

To be perfectly honest, is it really worth a black eye and a few broken ribs at best, and internal injuries at worst? Sure, you could sue them, but why risk injury (even permanent injury) when just walking away is also an option. It's not surrender, cause he will still own the car (even with its crappy paint job), it's a strategic withdrawal when the potential loss in a confrontation is unacceptable. Even Sun Tzu would agree.

He may not have liked it one bit, but he did the smart thing. A bruised ego heals a lot faster than a missing eye.

Meanwhile, he can name and shame the garage with every new person he meets without directly confronting them and show the car as evidence of the crappy job. A missile is a safer option than bayonet.