I am not doubting that this is what your stateroom host told you, but it does not make sense at all. In 7 months the Fantasy would have been at Grand Cayman about 15 times (she only goes there every two weeks). So, that meant that she would have missed the port two thirds of all the visits. I have read about people missing Grand Cayman, but it seems to happen far more infrequent than missing
Castaway Cay. I would guess last week was due to Matthew and that was quite extra ordinary weather.