National Park Service frowns upon "selling" these popular permits (i.e. basically anything in Yosemite, though other permits have been targeted). They're investigating ways to crack down on this.
You didn't buy a permit, so there's nothing to refund. The permit is free. You paid to make the reservation. Pass it on to a friend or inform Yosemite that you won't be needing it so someone else can enjoy the opportunity to hike up Half dome.