Have any of you ever gotten screwed by your medical insurance? Were you able to do anything about it?

My dad has been through several surgeries in the past few months and last night he had to be taken to Emergency because he got an infection from the last operation he had. Somehow, the insurance no longer wants to cover his stay at the hospital. How lame is that?? Isn’t that what they get paid for?? What’s the use of giving them money every month if they’re not going to help you when you need it. It’s not like we all have an extra 10k in the bank just in case we have to stay in the hospital for a week. At least not if you have insurance. You would think you wouldn’t have to worry about that stuff.