There is usually not very much holding truck cabs to the frame. A few air bags in the back and a couple of bolts and brackets up front. Just enough so not to shake loose in bumps.
With that said, my worst ever single truck incident was with B&B Concrete out of Little Rock when the floor of my cab in the old mid 70's pay star shook away and fall down to the frame rails a foot down at 70 mph on I-30 west near Hope.
Everything attached to the floor including me and seats fell down with it. Head was below the steering wheel and hood top line at that point with pavement going by just below the feet near the spinning shaft.
3 weeks and a few thousand rivets later they tried to hand it back to me.