Is one laser hair removal treatment enough to remove all hair on chest? Will it grow patchy or uniform on the chest area?

It is too early after one session to see results. Laser hair removal takes 6-9 sessions to reduce 70%-90% of the hair. This is because not all hair is in its active growth phase. Touch ups may be required every 6 months. Please consult with your treating physician if you have any concerns. 

Hair grows in different stages.  Laser targets only certain stage(Anagen) in hair growth cycle.  You need multiple treatments to target the hair at different stages of growth.  It will be hard to remove all hair with just one treatment.  It typically takes six to eight session to optimize the results.  

Hair has 3 stages of growth, an active phase, a transitional phase, and a non-growing phase.  The laser targets pigment in a hair follicle that is growing.  So it works really well on hair in the active phase of growth and on some of the hair in the transitional phase.  It does not affect the hair in the non-growing phase.  Not all of the hair on your body is in the same phase of growth at the same time.  That is why it typically takes 6 or more treatments spaced about a month apart to get a good result from hair removal lasers.  The hair hasn't grown back yet because what is left is still in the non-growth phase.  You are likely to see more hair as time goes by and more hair enters the growth phase.  That is why most practioners recommend a course of 4-8 treatments a month or so apart.  It is not possible to predict how the hair will grow back(patchy or uniform) since it is not possible to know which hairs are in growth phase at the time of treatment and which are not growing.