You would think the OP would be able to tell the difference of the Tire and Tire mount assy vibrating loose and falling off or not...
I know there are some photos online of the whole rear bumper mount assy coming off but you would think you should be able to see the localized damages caused by something like happening...
There really isn't much holding a tire assy to the bumper as shown in this photo... I only see a couple of bolts laying on the ground this guy removed to take his bumper and tire mount off.
Google Image
Glad he was able to get to safe place off of the road to get repairs.
Roy Ken