IIRC (it's been more'n 10 years since I have been at that plaza - and it was much smaller with no deck then), 50 runs beneath the Seven Corners intersection itself, while 7 is up top. 50 has no lights there, just offramps, but 7 has lights - is this correct?
If so, and if the car left headed east on 50, my impression of this guy having intimate knowledge of the DC area highway system would inch closer toward a realistic issue.