Generally, the 2-hour limit for non-permit holders is until 8pm. Aside from the official parking regulations, I think neighbors would have noticed and commented on an unfamiliar car being parked on the street overnight. I'm a personal assistant in a similar neighborhood in DC (Forest Hills) and my boss lets neighbors know when he's expecting people to be parking in front of his house. It's entirely possible that neighbors did tell LE about an unfamiliar car and that information hasn't been released. Also possible that nobody noticed but the fact that they did notice the vacuum cleaner salesperson, etc., makes me think people there are alert to strangers.
Thanks for the info. I've only lived in the DC area for about 2 years, but I swear every parking sign has different rules!
If DW or "others" did drive there and street park though, and the ordeal started around 6pm, this means the car could have been out there overnight. I wonder if neighbors did notice, not that much could have been done though since parking restrictions were off.