Duel at Dusk crossed the finish line a neck ahead of Epic Drama in Sunday's fifth race at the GP West meet.
But stewards reversed that order after they determined that Duel at Dusk, at 3-1, interfered with Epic Drama, at 3-2, in deep stretch.
The race was the start of the Rainbow 6, with a new pool after two straight days with a single "take all" winner.
Bettors wagered $12,021 on the Rainbow 6.
The race was a $50,000 maiden claimer for 2-YO.
it was scheduled for 7 1/2 furlongs on turf, but run at seven furlongs on the muddy dirt track.
The winning time was 1:25.08.
Luca Panici rode Epic Drama for trainer Eddie Plesa Jr. Nik Juarez rode Duel at Dusk for trainer Ralph Nicks.