Claim denied, but Optum never sent me an inquiry letter or call

I've been getting treatment for a herniated disc since March, ended up getting surgery two weeks ago.

I just found out that Sanford has denied all of my claims (imaging, PT, etc.) because I didn't respond to an accident inquiry from Optum. My injury wasn't from an accident; it just happened randomly with no apparent cause. I have never claimed it was from an accident, so I don't know why an inquiry was even submitted.

They claim that Optum sends three letters and calls twice before sending a denial to insurance, but I was never contacted at all. I finally got someone from Optum on the phone who looked at my file and said that she could see that they never sent any letters and never called me. She couldn't tell me why they didn't contact me, but said that they couldn't approve my claims because I didn't comply with the inquiry. When I pressed about how I was supposed to comply with an inquiry from a third-party company that I didn't know anything had been sent to, when I wasn't contacted, she said that she'd have to talk to a supervisor and see if they could resubmit my claims.

Sanford is still saying that they are denying all claims based on Optum's inquiry. What happened here? What can I do? Is it a common thing for Optum to just….not contact people for inquiries? Sanford was giving me the runaround about why the claims were denied and it was my PT's office who explained that I didn't fill out the right forms for an accident investigation. They said it's pretty common for people to be surprised that there was an investigation, and that about 50% of the time it ends up that they were never contacted about the investigation.