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?
anything more than a "yes/no" answer is also answering the question "I am not authorized to enter the cockpit and do not know airline procedures to gain entrance, how can I convince the crew to let me in?"
If one pilot is out of the cockpit and they don't know how to get back in, I'm assuming they are under duress and landing alone.
anything abnormal in regard to the crewmember re-gaining access to the cockpit and that door stays closed until the airplane is landed, boarded and cleared.