Unfortunately the media is having a field day with this. The fact that the F/O says "thick foriegn accent" makes everyone think of ji-had trying to bust down the door. Could have been some Scotsman saying something about the captain is stuck on the Loo (try to picture Groundskeeper Willie).
It's just normal procedure that when someone leaves the flight deck, the only person that will be coming back in will be the crew member. It doesn't matter if someone else is calling up front or knocking on the door with any password. If it's not the crewmember, the door doesn't get opened. Does it matter that the Capt is stuck in the lav? No, not for safety of flight. I'd be laughing my butt off and making inappropriate PAs. As an F/O, I'd just like to get down on the ground just so we can get the poor guy out before he gets blue juice on his bum.