i wonder if the pax got confused and thought they had to disembark in SIN and clear customs or something… like the USA? Or perhaps they thought they had a stopover in SIN, and didn’t realise they didn’t? (they could have been at the carousel waiting for their bags!)
It seems unlikely pax flying Qantas Y would need to go to the bar… they have generous and free alcohol on board. Maybe they got lost or hadn’t re-set their time to local time?,
4 bags for two pax might suggest however they had some sort of status, so might be experienced? Strange.
Smoking? There’s a smoking area right by the QF departure gate for the a380 IIRC. So even if trying to get a last one in, they’d only be 5 mins late, not a no-show.
It might have been an urgent medical requiring a trip to hospital, and perhaps someone said ‘well let the airline know’, but didn’t.