Surprise bill for follow-up visit to emergency care

In March I experienced a pretty serious fire in my home, and went to the hospital (Cornell-Weill in NYC) where I was put on oxygen and treated for what were luckily minor burns. This was all pretty much covered by my Aetna PPO plan, with a copay. I was told to return in two weeks to check up on the burns and they basically looked at it and told me it looks good and gave me some bacitracin to apply regularly. Last week I was billed for 450USD by Cornell-Weill for this visit. When I asked Aetna about it, they told me that it had been mistakenly denied as an out-of-network visit. They revised the claim and now the amount has been reduced from 450 USD to 290USD, but in the EOB Aetna still does not say they will pay any of the amount. They say this is because of a “no-referral penalty.”

I’m a bit confused because in the PPO document, it says that in-network providers without a referral are treated as out-of-network providers, but even so, most out-of-network provider services which this could possibly count as have some degree of cost-sharing. The revised EOB still states that I am responsible for the full (revised downward) cost of the service.

Because the fire destroyed *everything* I’m really not in a position to pay what feels to me like an unfair charge. I am required to get referrals for my plan, but I assumed that a required follow-up to an ER visit would count as emergency care. Is this wrong? Should I have been informed that this might not have been covered by Cornell Weill? Does this count legally as a “surprise bill”?

Thank you!