has it been 1 week since your session or 2?
if it's been only 1 week, you are just getting in the window where you will notice. if it's 2 weeks you are just passed the point where you should notice (and still may).
if it's been longer than that, i'd say to see how the second session goes.
you might know this already, but your hair grown in 3 stages. and the laser is only affective in the growth stage. that's why it takes several sessions to get most of the lil buggers. is your facial hair pretty dense? perhaps you just didn't notice the first time becuase new growing hairs took the place of the freshly zapped ones.
stay positive, i'm sure you'll get results