As he was in Class A airspace it should not be so difficult for the authorities to confirm as to how he ended up at FL250.
SoCal
The fact he was in class A suggests that it was not some sort of altitude attempt and unlikely to have been a requested cruise level.
It is possible he was lifted up there. I can remember flying in a Citation 2 to Nice.
There were warnings of severe turbulence between FL290 and FL240. I warned the pax, reduced speed and expected the worst only to be embarassed by silky smooth air to a Nice landing.
Leaving for the UK now empty and taking the more northerly departure over the Alps climbing through FL240 all hell let loose. 45 degree wing drops, items flying around the cabin, severe turbulence like I had never experienced. The jet was almost uncontrollable. Asked for an immediate climb to FL320. at FL240 the Citation 2 normally climbs at around 1000 fpm I had 4000 fpm all the way to smooth air at FL320.
This poor guy was hardly up there in a mooney by choice? any other ideas as lift could be one theory?
Pace