My sister left our refridgerator door open for nine hours!

All else being equal, for instance, assuming the appliance wasn't already on its last leg, that shouldn't have damaged the thing a bit. In fact, depending on the ambient temperature of the room housing the refrigerator, the density of the food in it (how much, what sort, how fully packed the cooling compartment was), and the temperature of the stored goods prior to the door having been left slightly open several hours, I doubt much if any of the food spoiled - if anything mebbe that stored on door shelves, and that which was closest to the open side toward the front, might have approached room temp, but I'd bet stuff deeper in underwent barely significant temperature change.

All in all, I'd say you have far less to worry about outta this than apparently you think you might have.

Thanks!