The "throw" was probably just a stress reaction.

Ball pythons are most vulnerable while they are constricting and swallowing prey ... feeding time (live, p/k, or f/t) is instinctually a very stressful time for them ... they want to eat, but at the same time they don't want to be vulnerable to predators .... my guess was that for some reason your snake was startled as the strike was occurring and "flinched" causing the "throw" ... spectators maybe???

-adam