I am glad you are not in the UK. As you would not have been allowed to push back with that passengers bags still on board.
In UK If a passenger has turned up at check-in with bags and somehow not turned up at the gate then regardless who they are their luggage that's still in the hold should be removed before the planes depart.
Didn't the same thing happen in the Locerbie bombing?
Bags can only travel unacompanied if it has had more instensed screening by the security agents along with their signature. 1 Copy for captain & the other copy for Dispatcher.
However this is another topic alltogether.