That actually happened to me, on a fleet Ford Focus. I was assigned to do a routine scheduled service. While moving the car from the back parking lot to my work bay, the steering wheel came off in my hand.
As far as I know, nobody had ever worked on and/or removed the steering wheel prior to the incident. I spent considerable time looking into the car’s service/repair history.
There was no discernible steering column damage. The threads were fine. We drowned the nut in blue loctite and torqued the heck out of it. That was several years ago, and the vehicle’s been serviced several times since then. It’s never loosened again.
Of course, it’s also possible some mechanic DID work on the steering wheel and/or column, and for some reason did not want to be associated with the repair. In other words, maybe somebody ________ the pooch, knew it, and kept quiet about it