PG, through amazing technology, Nick was in an isolation area in Kansas City. A robot was set up on the mound in Oakland. Nick had a mound built for him and simulated throwing the pitch, well actually threw the pitch in the isolation area. The robot delivered the pitch in Oakland to the catcher, literally at the same velocity and with the same movement of the pitch Nick was throwing.
While Nick was not in Oakland, his pitch was delivered to the catcher, one of the A's players who arranged this and will be visiting Nick when the A's head to KC.
Through additional simulation, Nick has a video which does not show the robot, only Nick throwing out that first pitch, and getting a chance to play baseball, the game he loves.
Hope this helps.