Logan could easily spot a liar and it was satisfying to him that he could tell Josh wasn't lying. The same way he could also, with his heightened senses, smell the fear and rapid beat of the boy's pulse. It made Logan more willing to forgive when Foley excused himself and nearly pushed back past him. He might have caught the boy and spun him around, but Foley had been verbally beaten in he figured and the cigarette was calming the otherwise feral mutant a little bit. Huffing another long drag before blowing it out the smoke stalled long enough that Logan felt comfortable leaving the john as well. He didn't want to leave immediately after Foley. It would be too awkward and look like they had left together.
When he was about to reach the door, still partially swinging from Josh's exit, Logan paused. He was more likely to get caught smoking in the halls and he really didn't have anywhere else to be. Logan leaned against the wall and decided to take a moment to enjoy his smoke. It'd be an added bonus that he was now positioned to yell at or scare off any other student that decided they needed to take a leak. Ah, privacy.