You were lucky that they didn't notice you had left the airport. They are supposed to check for that as a security measure and confiscate your bag. Not sure how the checking is done, but flying out on a CX flight certainly gets your name into lots of computer systems. I would never trust to leave my bag at the lounge while flying to TPE. Would be sad to come back to little pieces of debris after they had taken and exploded the bag (btw not a pedantic point, this happens to dozens of bags a year in the US, confiscated as possible explosives and destroyed as part of the defusing -- the saddest one was to a chinese inventor of electrically heated shoes who came to the US last year with his invention, TSA was not amused when they found shoes with wires and batteries attached and blew his invention up at SFO on the tarmac).