As soon as her situation got bad he/she should have been alerted and immediately plugged in. But, if he/she wasn't on the floor he would not have known.
I think that if you look at this in real time (and not Monday morning quarterbacking) by the time it may have dawned on her that it had become a real issue it was almost immediately over. She was too busy trying to sort the problem out rather than call the Supervisor over. Perhaps it's different in the USA but where I came from Supervisors did not generally monitor control positions unless requested to do so.