Maybe the passenger reference was to Lauren. Remeber when she went home after meeting with Kendall for the first time? And she saw Vaughn with Lauren. At the time she didn't know her name but maybe she mentioned her to Lazarey. She was Vaughn's "passenger".
Now that I have typed it..... it seems kind of ridiculous. But hey.... anything goes.
Ok, I think the passanger is Lauren.
I think this because when she and Vaughn got out of the car and went inside the building another car pulled up and had two guys in the front seat w ear pieces in. I also think that the guys were appart of the covenant and they were watching lauren as if she was on a mission.