That's one of the problems with easyJet they stuff their pax in corridors, jetways & stairwells. This is just so that they can say "boarded on time" & closed the gate on time....even if the aircraft hasn't even landed.
This is what can happened- the pax were basically abandoned.
This is the reason I only fly EZY when there is no alternative.
In the past I've stood in a stairwell for 25 minutes at Malaga, nowhere to sit, no toilets & then shoved on a bus making the speedyboarding useless. Never again !!
It should be of great concern that the aircraft departed, presumably with unaccompanied bags.
I prefer to fly with an airline that only boards when the aircraft is there AND the cabin is ready to receive passengers, this way it is rather less likely that passengers will be "lost".