I suspected you wanted for them to stick around, but I was trying to be logical. Bunji doesn't know who any of the other people are and he doesn't care, especially when he doesn't know if his mother was affected by the zombie attack or not. She's his priority. I was just acting in his nature. It can be assumed that that wouldn't be the last time that he saw them all, and so he could find out who they all are and blah-dee-blah later. He's already in denial about the whole thing and will probably wake up tomorrow treating the entire yesterday as though nothing unusual had even happened. It's just all too much for him to take in and just accept as though it's normal or "this is how things are going to be from here on out."