I have a collection letter from an attorney for a ...

I have a collection letter from an attorney for a medical device, probably legit, as my daughter had a knee injury a few months ago, but I don't have an invoice, Bill, phone call, etc. Looks like we skipped that part. I will go back through EOBs, but I'm amazed that my 16 year old has a collection letter before an invoice or phone call...I guess I can call the Google number to find out specifics, but they're pretty lazy as a business it seems...I have insurance and an hsa...pretty quick and easy to pay...IF YOU KNOW ABOUT IT.