I saw them again, yesterday. Through my kitchen window, I saw them walking across the street. I hurried outside and called out to them. "I just want you to know I have a 3-legged dog too!" I said. They crossed the street to meet me.
The lady, actually a young woman, is Amy. She is new to the neighborhood. The dog is Lana. Lana is a sweet German Shepherd. Amy adopted her as a tripawd, through a rescue organization. Poor Lana had previously lived chained outside as a guard dog, until one day she got loose and ran into the street. She was hit by a car. She paid with her leg, and part of her tail, but she earned her freedom and has started a new life with her caring owner.
At this point, I don't know when or if our dogs might meet. Lana, like Boomie, is not very friendly with strange dogs. But at least we know of each other's existence now, and that's a start.