I've had Delta cancel my award ticket before when I had my travel agent look at what the revenue fare was. She held the ticket, but didn't issue the ticket. The hold expired, but several days later I noticed my award ticket was gone. When I called Delta they told me their system automatically does this and confirmed it was the travel agent's actions that cancelled my award ticket. When I went back to rebook, the miles had gone up 20k... Frustrating to say the least and DL would not honor the original award mileage.