Sorry to hear that Mamy but the charity loses out especially if the setter bans all who question her error or who stop supporting the quizzes. Neither do I agree with the statement, 'the setter is always right'.
As most know I set quizzes and always check and double check my answers and will always allow a mark if an alternative answer is given which fits the clue or if I am proved wrong then void the question.
Unfortunately, in this case, the results/winners had already been notified so too late to amend even if setter was to accept error.