This didn't happen to me but a fellow barrel race with a Dolly Parton bosom.  It was when silk shirts were in style and they weren't easy to keep buttoned.  Running back from the third barrel her silky black blouse came unbuttoned one by one until they were all undone.  She was wearing a pink bra, riding a black horse and it was hilarious.  She laughed too and all the rough stock riders in front of the chutes totally enjoyed.

2 stories:

My cousin was running barrels at a playday and I seen something fall out of her shirt on the 2nc barrel! and she stopped and picked up what it was and just came out of the arena.  I asked her what in the world did you stop!  she said my boob fell out! and I wasnt gonna let the barrel guy pick

I was running poles and I knocked one of them over and tried to save it I ended up grabbing it and it came out of the holder and I couldnt make my hand let go and we had to weave again and I carried it all the way thru and handed it to the gate man!