Trading Spaces: The Locked Gate Episode

My horses have confounded me again. I am still scratching my head over this latest puzzle. Yesterday when I went down to feed in the morning Doc was is Pippin's paddock....and Pippin was in Doc's paddock. All of the gates were shut and latched. The horses had access to the stall that opens onto the paddock, but the interior stall doors were securely latched. No fence panels were bent or in anyway compromised.
My husband fed the boys the previous evening as I as away from home. He called them from their pastures. Each horse walked through his gate from his own pasture into his own paddock. The fence between the pastures is in tact, although it is low enough for them to jump and I suppose, if they really wanted to they might be able to play limbo going under it. However, my lazy boys probably did neither. And, had one thought to do that, they would have stayed together as they are best buddies. My husband does confess that he didn't look closely at the horses, and they are remarkably similar in size and color. The switch could have already been made when he went to feed, but he swears that he was not the one to swap the horses.
Our neighbor is a fun-loving guy and has been known to pull a prank here and there. However, he swears he did not sneak down to the barn in the dark of night to switch the horses.
Our son laughed a deep hearty laugh when I told him, saying that he wished he had thought to pull that prank on me, but alas, he did not. He also lives about 90 minutes away and probably has far better things to do than to drive to mom and dad's house to conduct a horse version of trading spaces.
So, I remain puzzled and intrigued. Ah well, it gives my feeble aging brain some exercise and perhaps will stave off Alzheimer's!