Could easily be wrong but an incident on the horse Clear Day comes to mind. (same horse who got up to beat Hyperno when R Higgins dropped his hands )
Not sure about the worst ride of the day but I'll give M Johnston the worst ride ever.
Poor Kingston Town, 59kgs and 50+ full blooded lashes all the way up the Flemington straight.
If only Malcom Johnston's brain had matched Kingston Town's courage.