In the late 80's I knew a bloke in Bundaberg who's son had lost his medical. The poor bugga had flown most of the day in Central Western QLD, not drunk enough water, not eaten, and fainted in the queue at the snack bar at Rocky airport.
The then regulator wouldn't let him fly for two (I think) years, because they couldn't find a definitive cause for the one-off faint. He had to attend independent neurologists to get the all clear before the regulator would issue a Class 1 medical, but they did in the end, and I think the chap concerned now files a white rat around.