What a relief! This is a prime example of the potential of being charged for and pressured into paying for something you didn't owe.
Good on you for pursuing the matter and getting it straightened out. Many would've been intimidated and paid. Human error can rear its ugly head anywhere and sometimes it's hard to recognize whether something is hinky or not.
We had a similar incident when we returned a car at Schipohl. There was a scratch on one of the wheels. Dolts that we were, we didn't look at the wheels when we rented it, so we didn't know if it was there then or if we'd somehow done the damage.
The over zealous young man taking in the car told us that the charge would be about €700 to replace the tire and wheel. And that the credit card holder would have to sign a form admitting guilt and pay that amount then and there.
My husband who knows a bit about cars, knew that the fee was way over the replacement cost. He asked what would be done with the tire and wheel that was replaced. The young man couldn't answer that question, so my husband said that he wanted them.
Silence. The young man was dumbstruck. My husband told him that if he was going to pay for the tire and wheel, he wanted them as souvenirs of the trip.
While this was going on, I called our credit union Visa people for advice. They told me not to sign anything or pay for anything. They would email me forms to fill out online and return to them.
By the time I reported this to the young man, he'd regained his composure and returned to his arrogance about the charges. He said it really didn't matter if my husband signed the form or not, they had his credit card number and could charge him anyway.
We went on to our apartment in Amsterdam. I got the email, filled out the online paperwork for the incident and sent it back.
A week later we flew home. A few weeks after that, we got the bill. It had not automatically been charged to my husband's Visa, and it was the equivalent of about $150. Oh, over zealous young man, so wrong in so many ways!
You can be sure that in addition to the normal thorough examination we do, including pictures, we have checked the wheels on every car we've rented since then, in Europe or the US.