He was impersonating a PA student, not a PA. That's not all that hard to do, depending on the hospital. A lot of the time students are expected to be completely clueless as far as how the hospital is run. So if he wasn't 100% clued in to how things work, that wouldn't have tipped anyone off. Side note: one of my ID badges as a student said "PA" not "PA student", too, so I doubt he had anything to do with what his ID said.
As a student I had several situations where I was an "outsider": the only student not from a given school, or I started my rotation at a different time than others, or never received an orientation that other students got. I'd constantly have to ask other students/attendings questions about simple day to day things. I was sometimes the only student who had to create my own work schedule or call schedule due to being an "outsider". I didn't always have access to "restricted" areas/info that I was supposed to have access to. My ID badge didn't let me into certain places and my computer account was restricted due to error or sometimes because nobody knew what to do with PA vs MD students. I'd either have to harass IT and/or security or constantly have other people help me into restricted areas or access info.
Of course all his "patients" received appropriate medical care. He was acting as a student, not as a PA-C. He didn't have the final word. All he had to do was learn how to do a basic PE, SOAP note, and present.