This very same thing happened to me this morning on the way to work....I pass by this corner house with a brown pittie/lab mix in the backyard everyday. Anyway, I saw the dog running loose just a street over from her house. I went and knocked on the door of the house, and a lady came out. I told her I thought her dog was out, and as she went to close her door, "Honey" came up the driveway....she was wagging her tail crazily but she was cowering, sort of, too....I really think she was just really scared and skittish about being out of her yard. Hopefully, the lady was nice to her....she seemed to be....so, I think maybe being loose makes the poor dogs extremely scared, nervous, etc.