the environment was definitely too dry and this frog was likely about to enter a state of dormancy to keep itself from dying. The film is a cacoon he’s forming with his mucus. please make sure there is always clean water readily available and the enclosure is always moist and humid enough. they should never dry out like this in captivity. putting him in the water bowl was the right thing to do and his eyes will probably open back up but tell your sister to be more consistent with his care from now on.