The latter did not refuel himself, it was a line boy who after the accident felt deeply disturbed for mishandling the fuel. Bob then asked the boy to refuel again for the rest of the airshow
That is indeed true, Hoover talked to the lad as he was about to drive away following the refueling and never noticed the truck had a "Jet A" prominently displayed sign, nor noticed the refueling slip had "Jet A" as the fuel dispensed, no mention made of a fuel drain being made. As you say, Hoover was most magnanimous following the event,
Hoover asked, “Where’s the line boy who serviced my plane?” Everyone seemed reluctant to tell him, apparently afraid that the airshow performer wanted to chew him out or be unkind to him.Finally, someone said, “He’s outside.” Hoover quickly located the boy, standing by the fence, with tears in his eyes.
Hoover went over and put his arm around the youngster and said, “There isn’t a man alive who hasn’t made a mistake. But I’m positive you’ll never make this mistake again. That’s why I want to make sure that you’re the only one to refuel my plane tomorrow. I won’t let anyone else on the field touch it.”
And for the remainder of that weekend’s air show, the young man refueled Hoover’s P-51 without any further incident.
When the National Transportation Safety Board investigation (LAX78FA053) concluded, its probable cause agreed with Hoover’s assessment: the improper servicing of the aircraft by ground crew personnel with the inappropriate fuel grade. Contributing to the accident, however, was the pilot’s inadequate preflight preparation and/or planning.