Hi everyone,
I appreciate all of the responses. I would have to say that I put more of the blame on Thrifty in this situation rather than AMEX, since they seemed to be willing to pay upon receipt of some documentation. I think at this point I'm just going to have to pay the $62.50, so that I don't get a blotch on my credit report from the collections agency.
I think in the future, I would report any damage to the rental agency and ask how they bill before I talk to AMEX.
Unfortunately, I have to continue to rely on the AMEX insurance because I don't have a car and thus no car insurance to rely on for primary protection. That's why I pay the extra $19.95 per rental to AMEX for the Premium Protection since it then becomes your primary insurance.
I'll live and learn, I guess.