The racecourse at Sandown Park also houses Sandown Golf Course and the Sandown Park Golf Centre, which could offer an explanation as to how the ball ended up on the track.
Clerk of the course Andrew Cooper admitted the freak incident was unavoidable due to the circuit's close proximity to the golf centre.
'With a golf course within a racecourse balls are bound to stray, and we take all reasonable and appropriate measures to remove them,' he told the Racing Post.
'We find them regularly and on a raceday, but the reality is when the grass is four or five inches long you often have to step on a golf ball to know it's there.
'Thankfully, while we do see one flicked up once in a while, I can't think of an instance in the last couple of years and I've never seen it happen with that sort of consequence before.'
Following his earlier fall, Fox picked himself up and rode First Experience to victory in the Kingsway Claims Fillies' Handicap later in the afternoon.