My nephew recently had a Sunday evening return flight from HOU to ATL on Delta. The plane he was supposed to fly on had mechanical issues so it was canceled. Knowing that he had to get back to his military base in Alabama that night, he purchased a ticket on Spirit, switched to IAH and flew to ATL. Delta was contacted last night through their Facebook portal and they recognized that the return ticket had not been used and that there was a balance left on it. The agent said he was eligible to receive the remaining balance. We wanted to find out what the balance was, but the agent said he wasn't allowed to give that information out to my nephew and he would find out what was left when he booked his next Delta flight and gave the booking agent the unused ticket number. Has anyone ever heard of something like this before? I figured that they would place the remaining balance in his Skymiles wallet for future use. Thanks for whatever information you can impart. Just trying to gather some information before we contact Delta again.