Why didn't your friend do what Airbnb suggests on their booking confirmation and contact them within 24 hours of arrival when the accommodation is not as described. One set of keys for 10 people is ridiculous. @An65
If the host wasn't willing or able to fix issues that meant the listing wasn't as described, you could have had Airbnb cancel and help you find somewhere else.
I am really surprised anyone would have stayed when you were given dirty mattresses on the floor rather than what presumably were beds that were shown when you booked.