Shayne you've been amazingly unlucky to have suffered this. Discs came out in 50's and I've worked on them since then and have never seen nor heard of this. I just drive off after making sure the brakes work and then get a feel of how they perform and drive accordingly. They can fade easily though especially if you put new pads on a rutted disc.
I guess the new pad may stick to the disc more easily than when a glaze has formed on it after some use. Air in the system would be irrelevant. There is no pressure in the system with your foot off the brake pedal as the system is vented through the master cylinder to atmospheric pressure.
Did you check that the wheels span freely after fitting?
I'm with Frank on the bad luck factor of this event, I've never come across this happening in all the years I've been fitting new discs and pads to cars.
A true victim of circumstance IMO. But it does remind us all that new pads do need to be run - or bedded in, as do tyres and clutches.
Hope all is well when the truck returns Shayne, don't want you having any excuses not to turn up next month
