Just a suggestion, but your car rental return will most likely be time-stamped so you can offer supporting evidence for being at the airport a long time earlier than 2 hours after the flight.

Not proof positive I agree as you could have wandered around for a while but it should show that your claim to have been at check-in 75 mins before departure is at least feasible.

Similarly as per the other post, your call to the AAdvantage Service Desk should have been logged as well I'd have hoped.