I think it's touching, and responsible,that you're concerned that your getting sent home left the rest "understaffed" and the sister was "flat-chak" ( I like that phrase) with work. The sister is "flat-chak" with work because she accepted the calling - she can handle it - and if she can't she believes, and who are we to argue, that the Lord will provide.
Still, if they are understaffed,they NEED you well. I'm sure they did it just as a precaution.
My wife goes to a nursing home three or four hours every day. She is not an employee, or even an official volunteer, but she often helps out serving lunches to the residents.
Sometimes she winds up serving ALL the lunches in the cafteria after they're brought from the kitchen because employees who are ill are not replaced with substitutes, it seems, by nursing homes.
I do not know your circumstances, but I know that most of the workers at local nursing homes, with the exception of RN's and administrators, do an incredible amount of work for a relatively small amount of money. It is important, vital, work.
Not too long ago the workers, not the RN's or administrators, got together and got my wife flowers and a card in appreciation for all she does to help out. Coming from these people, this was quite an honor. What I mean is that, generally, the workers in nursing homes everywhere are so busy it is difficult to find time to do even what they have to do for the patients.
Believe me, you have nothing to be embarrassed about. Perhaps you did look at some "idiot box" entertainment to "keep you going", but I can see you're far from an idiot.