Wasn't able to find an answer to this when searching...

I have an RPU that cleared. If this RPU is canceled, does the space go back into R/RN inventory? My guess is no, but I wanted to check.

The reason is because I want to apply a second e-cert to one of the passengers on the itinerary that I didn't do during booking, and UA says I would have to basically start over to get that applied, meaning I would lose the cleared upgrade and have to see if it clears when we rebook. If it goes back into R/RN immediately, it'll be worth it to try and do this, otherwise too risky.