Many years ago, I had a United flight fail to post to my FF account. I called them and they insisted that I hadn't flown - I was a no-show, so no miles. The agent said "I can't change the system to make it appear that you've flown, but I can certainly change your unused ticket for you. "

I think the change fee was $50 at the time and you didn't immediately lose all ticket value on a no-show...basically the agent was acknowledging that somehow the system screwed up and she was giving me that original flight, sans miles, for $50. I thought it was funny that they couldn't just accept my original money and post my miles...it was a semi-expensive ticket, not one that a mileage runner would buy, purposely no-show, and then call to claim they really flew.