If u have lost one... come to airport Egate Enrolment station at the departure lounge and ask for a new one. A new card cannot be issued unless the previous card is cancelled.
It doesnt take much time as ur personal data is already available in the system. Just the matter of printing a new one is all it takes but you will have to pay the fees (same as u apply for a fresh card).

Sys Engr
Airport Immig & Security