[Tristan Lall]

To the extent that past practice is a guide (because this isn't specified in the manual, and I haven't reviewed scorekeeper training materials in several years), scorekeepers can change the score to correct an error on their part, or because the head referee asks them to. Either way, they'll do it in consultation with the head referee and announcer to make sure everyone knows what's going on.

The head referee will only ask to change the score if they're convinced that a scoring error was made. If the referee could not be convinced, then you don't really have any options left. (You can advise FIRST of the error; they may or may not take subsequent action.)

From your description, I don't see anything unreasonable about the approach you employed, even if it was ultimately unsuccessful.