Unfortunately I had shut the stable door after the horse had fled.
Unfortunately, it's a little like closing the barn door after the horses have fled.
My horse backed in terror, reared, and fled from the bridge, throwing me sideways onto the road.
The charge turned into a rout and several horses fled ahead with empty saddles.
His horse veered off the road and fled with a frenzied gait, disappearing past the edge of the glass.
Or this: "The barn is empty when we return and the horses of our youth have fled."
To lock up young car thieves is another example of bolting the stable door after the horse has fled.
The horse threw its rider to the ground and fled.
They knelt before him in the snow, while, screaming in their fright, the horses fled away.
The horse got up and, squealing, fled its immediate danger.