Something to consider is that the museum pays for insurance. The insurance company might not be willing to cough up any settlement much less one based on the stated value of the photos without a law suit being filed. That leaves the museum holding the bag without the suit and they can't afford that kind of money I'd bet.
I agree that there is no excuse for losing loaned items. It's very sloppy and should deter anyonme who would otherwise loan items to the museum.
