I just read your article in the Washington post and thought maybe I could help. I was walking my dog last night around 8pm and saw a small beagle looking dog walking up the street. I was walking my dog at the time and thought maybe it was a stray so I turned around and walked back to my house because I was not sure if it would be friendly. I couldn't see the dog clearly because it was about 9-10pm but could tell that it was a dog and not a cat and was black and brown with a whiter face. I know the last possible sighting was in NE but I live in Chevy Chase DC and saw the dog near Chevy Chase Parkway and Jennifer Street, about a block from Connecticut ave (near the chevy chase circle). I will keep my eyes peeled tonight. Hope this can be helpful!!
Here is a link to a Google map I created where I spotted the dog and some details. http://maps.google.com/maps/