I've never seen a CA agent tipped for anything. I suppose if one really went out of their way to solve a reservation problem for you, or if they assisted you in carrying your luggage, then maybe a tip might be appropriate. But then I've never seen one assist with luggage either.
But normally, no, they don't get tipped and shouldn't be expecting a tip.
Could they have been waiting for another passenger to get to the elevator? Or maybe they were having trouble with the key to unlock the elevator to get it to go down to the track level?