Three Cats dropped off at vet office

On Monday a coworker of mine asked me if I could take in 3 cats that were dropped off at her job. She works at a vet office and she said she would have taken them in herself but she was redoing her house. My bf and I agreed to take them in and rehome them. She told me that these cats were patients and she knew the owner. It just breaks my heart that people do this to their animals and if I didn't take them in they were going to be put to asleep. There are two tabbies which are brother and sister and I think the third one is a Maine Coon he is shaved. The girl tabby has been hiding since she got out of their carrier and her brother has warmed up to me very much and is eating and using the cat litter. The Maine Coon I don't think comes out under my bed for food but he does come out to use the cat liter. I'm worried about the Maine Coon and the girl tabby. How long should I let them hide for? I don't think she has eaten since she started hiding. Any advice would be grateful? 

How lovely you took them in. I agree: It is such a shame people do this to their pets.

Have you tried placing food and water near their hiding place so they don't have to come out to eat and drink? If they are really scared it can be a good idea to confine them to a smaller space, such as a bedroom. They will feel more secure there.

She is confined to my bedroom and I tried putting food near her hiding place and she still hasn't come out. The Maine coon has been coming out today and been eating and using the restroom regularly.