A traveler who used his American Express card’s collision damage waiver got stuck paying nearly $1,300 because of a missing document. Whose fault was it?

Dear Tripped Up,

In April 2024, my wife and I reserved a one-day car rental to travel from Lisbon to the Shrine of Fátima, about an hour north. We made the reservation through Enterprise, but it turned out to be with Guerin, a partner. I declined the optional collision damage waiver because my American Express card includes a similar waiver as a benefit if I pay with the card. At some point during the trip, the rear of the car was damaged — I’m not sure how — and Guerin charged me 1,205 euros, then worth just under $1,300. That May, I filed a claim with AMEX Assurance for reimbursement. Among the documents it requested was an “itemized repair estimate,” but despite my repeated requests, Guerin did