Did you try to go directly to the cafeteria and were refused? I'd bet the security guard was there to prevent people walking backwards through the store and stealing, though I assume they purposefully placed him in an area to make people think they couldn't walk directly to the cafeteria.

Yes, he explained that the passage there is only open during emergencies or something like that.

The answer to this is always "well, this is an emergency for me, feel free to call the police if you mind me going to the cafeteria".

I wonder what it feels like to be the human equivalent of a door.