Keep your records

Do you keep all the records sent to USCIS ? If you don't, does your lawyer have a copy ?

Get a copy of the records from your lawyer. I don't think they can deny you on this. You tell them since you are not doing what I want to do, I'll do it myself.

Check the copy of your medical exam, and the date it ws sent. If it was sent by FedEX, there should a receipt for this. Attach the copy and recipt send it to USCIS by registered mail to indicte you did sent the medical exam to them. If they still insist they don't see it, you can only redo your medical exam to reduce the delay.

Or just redo the medical exam and send it with all the history by registered mail. Now, you'll know if they received it or not and they won't have any excuse.