What the actual fuck, does he only have one pair of boots, or if the insert has been added to counter a previous problem did no one think to try in in training.... And take it out if causing pain?
Either total bollocks or very tin pot.
He has orthopaedic inserts to correct an issue with gait (perhaps he has one leg longer than other, over pronation, etc). The insert "failed" so stopped working correctly - therefore Thompson got pain in his leg somewhere. He changed boots, but the damage was done and he couldn't shake it off.
Hopefully its one of those that you wonder what the hell happened two days later because you feel absolutely fine.
Have to say I empathise with Thompson. He's doubtlessly doing everything he is instructed to do on fitness, strengthening, flexibility, motion and the like. Yet he's still brittle. I'm exactly the same these days, though I'm 43 so have that excuse. None the less its incredibly frustrating.