i think its best the op go down to sq local airport office and see the station manager personally. I don't know about bne but sydney has 4 airport managers, 2 seconded from singapore. So long as print proof is produced, its very hard for them to push you away.

If you really want it to be really answered, then send a registered post letter to their sq sin office. If the crew supervisor noted your complaint, then the sin office will entertain your request, if no notation was made by the aircrew, YMMV.