I haven't read all the posts but...When we had our Fifth Wheel until 2006, there were many reports of stolen trailer tires. Seems most of the tires from the factory didn't last long. Our's didn't; Goodyear Wranglers.
So I suspect that was the reason so many were stolen.
Batteries and boxes on the outside back then and even propane tanks and bikes on ladders etc.
And... we still see coolers and chairs and ladders and septic drain lines,but not so many tires, on the shoulders and more so in the medians of the Interstates.
Since his mount was missing too I would suspect theft. I haven't looked at many spare tire mounts on Trailers in a long time so I 'm not up on what might com loose or give way. Most new ones, tht I've seen have spares underneath somewhere or none at all.
If in fair health and a little time safety break cables could be ingeniously placed around a spare or things and underneath to a loud alarm and battery.
The better and or larger RV parks now have gates and no one in and out during the night. Of course a lot of these tales or instances seem to revolve round, some Campers laving as soon as they can and perhaps taking some of our goodies.