Agreed that the pilot definitely made a huge, and not really reasonable mistake. Even though it was pre-9/11, I'd expect a pilot who was going to fly in/around DC to know there's going to be restricted airspace and to take the time to understand it.
(if link doesn't work, go to the Wikipedia article for Ronald Reagan Washington National Airport, and look at the bullets under "Expansion and restrictions")
Runways and named by taking the degrees from magnetic north and dropping the last digit. Parallel runways will be designated (for example) 31L(eft) 31C(enter) 31R(right).
You'd need to rotate the runway to rename it.
This story is from the early 80s. The magnetic north pole moves around 40 miles per year. What was once runway 18 at DCA over 40 years ago is now 19.