Cannabis only causes mild pupillary constriction. There've been several studies on that. If you or your friends were also using other substances or drinking (Don't confirm or elaborate on this if you respond. We have a cannabis-only discussion policy here.), that might have been what caused your constricted pupils.

When you checked on your pupil size almost 10 hours after smoking, were you by any chance facing a bright light or brightly lit mirror? I'm guessing that was what your pupils were probably reacting to.