If you don't show up for your reservation, the restaurant doesn't know why you didn't show up, just that you didn't. They'll mark you down as a no-show.
You can make a call to the cancellation line or drop into a Guest Services and try to have the charge waived. It might work, but it might not. Once you make a reservation with a credit card hold, you're expected to do what you need to do in order to make it to the restaurant; on a day when capacity closure may be likely, that might be to get to the park early and don't leave it before your reservation.