Well if the program wasn’t edited by you, and the client wants to make a change…in this scenario, i would suggest you tell the editor to make the change and update your list and media.
That is not uncommon at all. You are coloring a show, and they make some changes.
Tell the client
“Once the editor updates everything, i’ll incorporate it into the program.”
your other option would be to ask the editor for an aaf with embedded audio, but that would cause a lot more audio work on your part.
Asking a mixdown/output of someone elses media to be able to revert back is a pretty big “wishful thinking”
Information like that does not travel with an outputed master file.
Glenn