Markham Road. Exit 44 off of 66 heading west from DC.
Regarding the cop thing, I think it was amusing. He probably saw the tire tracks in the parking lot that looked like they were made by a Civic LX, and thought, "These could be the jackasses."
I think a lot of cops are gear heads. A few of my colleagues at my last place of employment enjoyed cars just as much as the next dude.
In CA, a few higher-end tuners hooked up cops who brought in their cars for tuning and modifications. I don't know if there were additional perks included.