Thank you stranger for the quietest warning I have ever had

I was wandering the walking street at Fisherman's Village in Bophut on a Friday night. Someone passing me said, very quietly, your fly, and kept walking. They did not stop. They did not turn around. By the time I looked up they were three stalls away. I fixed it in a doorway. It was the kindest possible way to deliver bad news, and I have thought about it every day since. I walked the rest of the street like a person who had been protected. I bought a lantern for no reason.