You could no-show, as the poster above suggests....But I think the courteous thing to do would be to call, or go to the transfer desks and tell them that you can't take the last flight because you need to be in Hong Kong. It's not the hugest deal, but it will be a nice thing to save the gate agents the added trouble/stress of trying to track you down while doing everything else they need to do to get the flight out on time.