After about five minutes, the woman went over to the second window and said, "Excuse me, but do you know what happened to the man who was helping me? I asked for stamps 10 minutes ago and then he vanished."
The employee paged him. Another few minutes go by and he didn't appear. The employee paged again. Magically, the man returned to his window. I was just about at the front of the line at this point, but I couldn't hear what he said to the woman. I did, however, hear her say, "You had to go move your car? Are you kidding me?"
Apparently, it's OK to ditch a customer in the middle of a transaction to go move your car. Who knew?