Is it plausible to forget the cockpit unlocking code? Is it plausible for a pilot inside the cockpit to be incapacitated and that at the same time the pilot locked outside simply doesn't remember the code or the procedure for entering the cockpit?
The code would also be shared among the purser and/ or the other flight attendants, so the answer is no. I believe however that they tend to keep the same code for a few days within the same crew to make remembering it easier.