Something similar happened to my parents a long, long time before I was born (early 1970's), when they were living at the edge of the Superstition Mountains in AZ. My father was away at work, and my mother was out tending to her cactus garden and watering her lawn (the only one with grass on the whole street), when she heard a VW bus traveling at a high rate of speed and kicking up a huge plume of dust down their dead-end road. Beyond the road was nothing but open desert.
The occupants of said VW were of Mexican descent, and the van was very nearly overflowing with said humanity. Very soon in their travel down the street, they noticed the road was a lot shorter than they had originally perceived, and tried to enact countermeasures by trying to turn the bus, without braking, to avoid flying off into the wild beyond. This didn't work out so well, and resulted in an enormous amount of commotion and mechanical protestations by the VW, all the while with the visual portion of the spectacle being obscured, because in an instant, their road dust plume overtook them. Not to be outdone, the desert answered the road dust plume with an even larger plume of it's own, obscuring any and all possibility of seeing what was happening.
One minute before all of this, as I mentioned earlier, the bus had a figure that my mother wagered to be about 15 or so passengers inside the dust shuttle. Two or three minutes later after the atmosphere cleared, there was not a single soul to be found in the bus, under the bus, on top of the bus, or anywhere near the bus, aside from my mother. The bus however, had managed to perform what would arguably be the automotive equivalent of a three-point landing, by bursting all the windows, and landing perfectly on its roof, with the entire rest of the body completely and utterly unscathed.
My mother called the police, and of course, when they showed up and began questioning some of the Mexicans that lived on the street about the whole affair, it was found that no one had seen anything, heard anything, or had any idea whose bus that was, or had any idea how it had managed to get upside down all by itself.
Since my father was an amateur photographer, he always had a camera with slide film loaded into it laying around the house. Before the police arrived, my mother snapped a photo of the bus, looking very forlorn on its roof, and all by itself in the lonesome desert.
Hopefully when I go over tomorrow to help cook dinner, I can find it, and scan a picture to add to this thread. It is my favorite slide of all 20,000 or so that my parents took, and it is known in the family that whenever my parents pass, I retain sole ownership of that slide.
