John,
Cabbies in D.C. can be of the "don't know where it is" frame of mind when it's somewhere they don't want to go
Cross town from the hotels in NorthWest DC is somewhere they don't want to go. They can't get many return fares from over near the Arb., which is probably why the fourth cabbie waited for you. He was certainly gracious to wait. He certainly didn't have to do it.