Something I've been trained for on heavy equipment, like tractors, is that you NEVER turn the wheel back up a grade if you are starting to turn over. You are supposed to turn down the grade to prevent a roll. So, if that was the case here, a slight off camber with a wind and the driver corrected by turning back up the side slope due to ruts, then the momentum of the tip over is carried forward. However, if the driver had turn WITH the wind, and down the rut, it's likely he could have saved the situation. Of course, being aware that the situation exists would need to be realized. It sounds like he was surprised that the camper was even missing off the truck until his daughter told him it was.
Youtube has videos of tractors rolling on an off camber due to the front wheels turning back up the hill in an attempt to recover. I'd recommend viewing those so that we can all be aware of how to drive out of a tough situation if it happens to anyone here.