Read the article further. When the police called the phone number on the document, the person on the other end denied that they were authorized to be in the building.
I can’t understand how you think this is impossible if you do things “the right way”.
Phones gets stolen or dropped in the toilet. Your contact has been taken to the hospital. Bad cell service. And so on.
These episodes of Darknet Diaries were my favorite. Very suspenseful. I also always thought the people doing the testing were insane for assuming a piece of paper keeps them from getting dragged to jail or worse.
I mean this is stuff the security people tell you not to do. If you get an email from “your bank” saying “call us at this number”, you're supposed to independently verify by calling the main number, not the number they give you, right?