Maybe the proverbial horse had already escaped the open barn, but too late or not, his training kicked in.

Won't it be like locking the barn after the horse has escaped?

A rearing horse can also break away and escape from a human handler.

Then with great difficulty he turns, and his horse escapes without any wound or harm.

The loss fell chiefly upon the foot, the horse for the most part escaped.

"That horse has already escaped from the barn," he said.

It may be closing the barn door after the horses have escaped but it's all I could come up with.

It was only a wonder that the horse had escaped in ground so difficult for riding.

As usual, once the horse had escaped from the barn, the door would be locked and guarded.

The horse had escaped from his master's small clapboard stable in Brooklyn.