Health Care/Medical Question

I recently went to a doctor for health reasons, and he referred me to see another doctor at the same office. When I made an appointment with the other doctor, I was never informed that the new doctor was not covered under my insurance. Now, I've got an unexpected large bill from the doctor's office.

Is there any sort of law saying that they have to inform me of that sort of thing? I really don't want to be stuck with this huge bill. I assumed that since the doctor was in the same office, recommended by my doctor, and nobody ever told me he wasn't, he would be covered under my insurance. Obviously, had I known he wouldn't be covered, I would have seen someone else.