Have you ever had a gate agent pull the wrong flight segment coupon?

My business associate and I traveled EWR-ATL southbound on CO and back home on DL. In EWR, the CO agent pulled my associate's DL coupon. My associate didn't notice the problem until he arrived with his CO coupon at the DL podium in ATL. The DL gate agent sent my associate to the customer service counter, where DL instructed him to file a lost-ticket claim and charged him $743 for a replacement one-way ticket home in coach.

Now that he's back home, my associate doesn't relish the prospect of coordinating communications among himself and two airlines to get his $743 back.