Laser Hair Removal: Accuracy For Straightening Hairline?

Hi, i have had a single laser session (1 zap) to straighten the hairline above my forehead (male). After a week, I am noticing that the hair about 2 inches above the area also appears to be thinning quite considerably. How likely is it that my single session is affecting the surrounding areas, and is this permanent?! Probably a stupid thing for a guy to do, but the salesman was pretty convincing that only the treated area would be affected. What are your thoughts on the chances of regrowth??