I am not with fedex but i may be able to explain what you saw. As a solo with Panther from time to time they can’t get a truck to make a swap with.. either there isn’t one avail on route or the driver is asking too much to do the 2nd half so they will have you run it as close as you can then hire a local company to some out and take your trailer to the customer unload and bring you back your trailer to meet the time constraints of the customer.
Or it might have been something as simple as the FDCC contractor tractor broke down and with all others busy or otherwise unavailable, a local hauler was tapped to finish the run.
We were at a FedEx facility in California the other day and saw a Custom Critical dry van parked there among all the other empty trailers. OMG! Could that mean that a major move is afoot or something sinister is going on?
Or might it mean something like the trailer was parked there pending a repair, or the solo driver pulling it dropped off there before he quit, or, or, or.
All sorts of theories can be spun around sightings like these in the absence of other information; and there is no shortage of people who love to do so, filling in the blanks seemingly for the entertainment value alone.
In the case mentioned above, the only thing that can be said for sure is that a FDCC trailer was seen being pulled by a local tractor. We don't even know if that trailer was loaded or empty.
In my military days I worked for a time as a military intelligence officer (S2 shop in an infantry battalion). We were trained about the difference between what you see and what you think. You might report that you saw an enemy patrol walking north when in fact what you saw was six men in enemy uniforms armed with rifles walking north.
You do not know if it was an organized patrol or six soldiers in retreat from a battle in which several larger units were scattered, or even if it was a special ops unit of friendlies dressed in enemy uniforms to make their way behind enemy lines. All you know for sure is that you, positioned at your coordinates, at this time of day, in these weather conditions, observed six men 400 meters away (your count and distance estimate), proceeding north on foot, carrying rifles. Whether the rifles work or have ammunition, you cannot say. A patrol would likely have working rifles, but you do not know it is a patrol.
As it is on the battlefield, so too it is in expediting. The more aware you are of the difference between what you see and what you think (and what you want to see and want to think), the better research you are inclined to do and the more accurate conclusions you are inclined to reach.