I've learned some hard lessons with this type of return system. Tho' I haven't been able to come up with a "fast" way of obtaining a receipt. I now take it as a mantra to take pictures of the car before and after from as many angle/directions as possible - exterior and interior. For the former - try include some background of the drop off area to show where the car was when you left it. For the latter - include a picture of the keys on the dash/seat/etc. as well as a good photo of the fuel gauge showing how full the tank is as well as the mileage/odometer.