Come on now... how many of you have gone to the biffy an return to the cockpit to find the cabin crew member occupying your seat? Any pilot who remained in the cockpit get turned in for that?
That is exactly what happened to a good friend of mine, an experienced Captain with a major UK airline, thirteen months after the event happened. (He had allowed one of the cabin crew to occupy the FO's seat for a couple of minutes while the FO had gone to the toilet. Simply that.)
Mind you it was just after 9/11 when he was called to the office, when they were using any method they could to reduce pilot numbers.
I believe that the individual who reported the event got his upgrade some months afterwards. Nice.