Fun Fun. Run the shit out of that bitch, then challenge it (I'm not actually advocating what I just wrote. Don't do it. But if you do find yourself with a ticket, I recommend reading 15.2-968.1 of the Code of Virginia).

Carry a camera with you though and go back to take a picture (or better yet if you have video do that) showing that there is no sign. There is a rebutable presumption that there is a conspicuous sign in place within 500 feet of the intersection. The state law requires that any locality using a red-light camera place such a sign.

My only thought is maybe they haven't done it because it's still in the 30 day grace period.