What happens if MassHealth decides that you're ELIGIBLE, but you're NOT ELIGIBLE?

For example, if you call MassHealth and they sign you up for Temporary MassHealth coverage, then you see your doctor, and then after that, MassHealh says, "Whoops, we overlooked something and you were NOT eligible in the first place. Our mistake, sorry!" Do you have to pay the full cost of the doctor's bill or will MassHealth still pay it?

Let's say you provided 100% correct information and the person at MassHealth simply goofed.

Has this happened to anyone on here?

(MassHealth just signed me up for temporary coverage, but according to every online document I can find, I don't qualify. I'm considering calling MassHealth back to confirm my eligibility.)