Seems like this is becoming a more common occurrence. It appears that there are companies out there that have convinced most of the Car Rental Companies that they are "leaving money on the table" by not pursuing damages on rental cars. I have heard of this from Hertz, Enterprise (possibly the worst offender), National, Budget, and Thrifty.
This includes the infamous "loss of use" clauses when the car is in the shop for repair.
However, looking at many of the cars that I have rented, if the rental car company is receiving funds for repair of "damage", they do not apparently actually repair the damage.
I have had letters for parking tickets assigned to my rental for a period three weeks AFTER the rental.
The $1700.00 charge might be a good candidate for a class action against this type of 'trolling for payment' schemes.