Credit card holders yesterday were warned about an elaborate scam in which people are persuaded to reveal their identification numbers to thieves after having their cards stolen in restaurants. Several cards have been stolen in restaurants in Kowloon City and Hunghom in the past week, police said. After the robbery, victims get a phone call from someone claiming to be a police officer. They are told a suspect has been arrested and the card recovered. They are then asked to report their loss to a 'centralised credit card centre', where they find they are asked to disclose their identification numbers.