" In that case, the bag would be removed if you just disappeared. I've seen that done. "
Saw it on American at LHR - two passengers got on (business) he decided after 10 minutes that he wasn't traveling and got off - the Cabin Staff asked his Mrs was he likely to change his mind - she shrugged and said it was unlikely so they collared one of the ground staff and the bag was found (remarkably quickly ) and trundled away.