If a passenger was left on board because he/she was in the toilet and the cabin crew didn't check properly, to be quite honest, they probably deserve a disciplinary. How could a crew together be collectively that unaware of the state of their aircraft? Why should ground staff be more aware of passengers in the toilet than cabin crew?
The cabin crew job starts at the briefing table and ends at the briefing table, regardless of what happens in between - tiring flight or not. If the environment is too fatiguing, this needs to be taken up with the airline and (failing it being properly addressed there) the CAA.
MF crew, all being experienced with other airlines, are much more likely to understand their responsibilities throughout their duty than crew who have been pampered by absurd union restrictions.
