Medical collections w/o ever getting a bill

[HipGnosis]

My dentist sent me to an oral surgery office(?) for a proceedure.
The proceedure was over a year ago.
I never got a bill from them.
I got a collections letter / notice!!
I double checked / confirmed I never got a bill.   I'm a math nerd and very organized.  I dealt with position & dept. budgets when I was working.  I didn't get anything from them.
The collections letter included steps to for me to request the original debtor to 're-send' me the bill.   I did that.
What else can / should I do?   What should I NOT do??
I'm not really concerned about a hit on my credit record or score.  My score is good and I don't use credit - but I am thinking of moving to a rural home / homestead someday.  I will get a mortgate if the interest is lower than my investment returns.

[bacchi]

Medical collections aren't really a problem with credit reports anymore if you end up paying. See https://www.consumerfinance.gov/about-us/blog/medical-debt-anything-already-paid-or-under-500-should-no-longer-be-on-your-credit-report/.

First rule of dealing with collection agencies: Never, ever, admit to the collection agency that the debt is real.
Second rule: Record all conversations with them. If you can't record it due to state laws or technology, write down the call date and time and what was said.

Also, it might be worth it to call the surgeon's office to see if you can pay them directly. You owe it and there's a chance they can pull back the debt (medical providers often have 2 levels of debt collection; the first level/agency takes a cut and passes the rest back to the provider).