How sweet is that!? What a wonderful horse!
My horse only had to go to the bus stop, but he did the same. He hopped a gate to get out, and let me open the gate to put him back in. Even though the knew he could get out when he wanted, other than the bus stop he only went out to round up my sister's runaway pony that went under the strand of wire in the creek, and once to come up the front porch to stare in the picture window.
He knew how to use a doorknob, and let himself in the basement through the open garage door one day. He'd also slobber up the doorwall trying to open it with his lips.