The right time to jump on it, is, whilst you are there.
At checkin, they will look up and check your stays at SIN, but that is no excuse, but sometimes as in any business, the wrong customer gets the attention.
Drop a note to the GM, express your displeasure, they normally ask that you contact them on your next visit. This is a very busy hotel, most visits I get a 2 room suite in the front tower, one floor up from club.