So you expected your doctor to call you directly and ask you to pay your bill? Um, no, they aren't bill collectors. As for what the bill collectors are allowed to be provided for purposes of collecting bills, read HIPPA. There's some information that people in the health community such as collections if directly related to the doctor they are collecting the bill for can know. But as to the extent of this, again, read HIPPA.
You have several problems here. It appears that your employer questioned if your injury was due to your job, or on the job when it happened, thus required many reports to be completed, (which) you failed to do. So doing some and not the others, then you in “effect” gave up. Now, if this had been deemed WC, then WC would have paid for all your medical bills while treating and also would have paid you wages if unable to work.
But, once they deemed not WC for lack of proof from YOU, then you (thought) that your health insurance would pay, but guessing that whoever treated you, did (not) bill your health insurance, since if they believed you that this was an work injury, then they would most likely bill your employer to submit to WC.
Now even if they did bill your health insurance, then your health insurance would NOT pay, since the bill was probably (coded) WC. But, once you found out that they denied the WC, then YOU would need a written denial from WC or from your employer that your injury was not a WC claim, then your health insurance could have paid at that point.
But, with most health insurance, you MUST submit the claims w/in 6 months to a year max and since this was 2016, it is very unlikely health insurance won’t pay, since you waited too long.
And no, the statement is not violating HIPPA, since this bill from collections is validating to you the bill that they want to be paid back.
So check with your health insurance to see (if) they might pay, but don’t be surprised if they say no due to the time frame of not submitting before and with (proof) of no WC.
I bet that you still have that stack of mail that you could have put aside and did not look at and in those papers will see numerous letters asking you to pay or proof that is still there.
Good luck, you will need it.