Well, mystery solved lol.
Seems the neighbor behind us had their son house sit while they were gone. They use to be rodeo people and my son had asked their son if he would ride the horse a couple of times, just exercise him a little, while he was gone. He has been keeping up with my son's progress and knew what was going on with the horse. But, my son told him to call me and let me know when he would be doing it. This all came to light when I picked my son up from camp today. And, when I got home, I checked the caller ID and my neighbors phone number was on the ID, apparently left before he rode.
So, I just jumped to conclusion and I'm glad that I didn't go storming over to the other neighbors house LOL.