OT - Airline ticketing

My son in law purchased a ticket for my daughter on United Airlines
using a credit card. The purchase was made on line. When my daughter showed
up for the flight, she was refused boarding because she didn't have the
credit card in her possession. The ticket agent, in Eugene Or., said "We
have to see the actual card, after all, it could be stolen". The agent did
say, that my son in law, a Marine, could go down to his local United counter
and show the card there, and the agent there would mark the box in United's
computer, so boarding could occur. The trouble was, United doesn't have a
counter in Al Asad, Iraq. The kid is coming home from a tour of duty in
Iraq, and the plan was for my daughter to get to MCAS Miramar to meet him.
After some very tearful "discussion", and I believe, a direct threat of
bodily harm from my wife, the agent allowed my daughter to board.
Has anyone here ever heard of this crap before? Aren't E-Tickets usable?
What was going on here?

Al G