Did you get a ticket for parking in a street-cleaning zone from April 12-14? If so, you might be able to get the ticket erased. Turns out DPW wasn't supposed to ticket anybody in the area bounded by H to Florida and 15th and 5th Street NW, so if you got a ticket there those days, give them a buzz.
The contact is Kevin Twine, firstname.lastname@example.org, 202-671-2593. Doh.