I'd call the service desk and ask where the RFE is in the system. Has it even been filed by the SL office? 2mo to put that in your file is weird. It's not like it's going through one of the main USCIS centers where paperwork is reviewed and approved. It's the SL officer who just puts the missing document note in the file to trigger the RFE letter. I called when we hadn't seen/heard anything about our letter after a week, lol.
We had the exact same thing happen in the SLC USCIS office. The interview was flawless until the end where we were told our medical didn't make it from London. Although super frustrating after getting so close, we made an appt with a civil surgeon that could see my husband the soonest (like 2 days away) to waste more $ on another medical and for a crazy Dr to sign off all the things that we did in London. We got the RFE letter about a week after the interview where we were told the medical was missing. We immediately put the new medical & RFE back in the mail and sent it back to the SLC office and in about 10 days our status was updated to approved and card created/mailed. Sorry it happened to you too!