Yes. I turned the car in and walked away. But I didn't buy third party insurance.
When you rent a car you are responsible for anything that happens to it. If you return it with a ding you have to pay to fix the ding and pay for the time the vehicle is out of service waiting for the ding to be repaired. Often your auto insurance covers this, however its a major PITA because (as you found out) they want the money NOW.