I would recommend that you call the hospital billing office. Advise them they you are attempting to help them get paid, and that you need their help in filing your claim to insurance. I would ask for a supervisor if the customer service representative refuses.
Likely, your claim will initially be denied for “timely filing.” That is where insurance states they didn’t receive a claim within the filing limit allowed. This limit varies by insurance company. The good news is that a denial at least means your claim is now on file!
Then, I would your insurance company and request that they reverse their denial. You can try this by phone, but may need to send a written request. Explain to your insurance that you were unaware that the claim had never been received, you had active insurance coverage, paid your premiums for coverage, and do not expect to be penalized for the oversight. I have found that insurance companies tend to waive their timely filing requirements when patients request (demand) it rather than the providers of service.
Advise the collection agency of your actions and let them know that you are working to get the balance paid. Then, be persistant!! It pays off. You will need to stay on top of it to ensure the claim gets paid, but it is not too late!