A user in our office has done this...
He added new keyed notes to the TXT file.
He than went to add the keyed note in Revit and realized it wasn't available because he didn't reload the TXT file, so he hit escape thinking it would cancel the command. What it does is leaves the keyed note there with no key value. This places a new #'d keyed note with NO keyed note text in the schedule.
OK... now were are these mysterious keyed notes?
I cannot select all instances and isolate because the element that is being keyed noted has to be visible.
I cannot think of a workaround to simplify this rather than scanning the model views for that 1 keyed note.
I have the pleasure of fixing all of these and he has done this what seems like on every view.
Has anyone figured this one out?