An incident

Training is an ongoing process. I have the bruises to show it.
Last Thursday, I took Zorro out for what I thought would be a short moon run. The weather has been insanely hot, punctuated by thunderstorms, so I take every opportunity to get Zorro out and about, and he's always happy to run when the moon is up.
As we hit the path, I saw a woman walking toward us with a small, short-haired brown dog. As I'm accustomed to doing, I pulled Zorro off the path and put him in a sit. I do this dozens of times every week and usually there's no problem. Zorro will look at the dog, but that's it.
Not this time. I think the dog may have growled at Zorro, or insulted his heritage in some manner, because the next thing I knew, I was flat on the ground with a face full of dirt. Needless to say, I lost hold of the leash.
Here's where it gets interesting: once Zorro got up to the offending dog, he stopped. He didn't jump on the dog, and the dog didn't go after him. They just stared at each other. I managed to right myself and put my foot on the leash before anything escalated. I apologized to the dog's owner, who said her dog was "unpredictable." A passing runner asked me if I was OK. I said I was, and continued our our walk, but when I woke up the next day I felt like I had been mowed over by a semi.
We haven't had any similar confrontations since then but when I encountered the same woman on Sunday, she turned around and went in the other direction. Meanwhile, I'm making Zorro do more sit/stays on his walk.