Enterprise Rent-A-Car Damage Claim Dallas Texas

Rented a car for less than 18 hours back on 11/1/13. When returning the car a small plastic splash guard under the car detached itself when entering parking garage. Informed the attendant great car except for the splash guard just detaching randomly upon entering the parking garage. Was informed by the attendant that it shouldn't be an issue and if anything I might get a phone call or an email about it. About a month later I received a bill for $445.49 for damage to the splash guard under the car!! Should have been a $25 fix for new plastic bolts. This is an area which is not inspected by enterprise or customers when taking possession of a car. It was likely loose prior to taking car from a company car wash and this was the first time it climbed an incline into a parking garage to make it loose. I rent from Enterprise 2-3 times a month and question if I should be doing business with a different company.