sure that this was a bee, there are flies which "imitate" the appearance of bees to scare of predators. and those flies are bad news most of the time.
if it was a bee it would be odd, since cannabis produces no nectar which attracts bees since it is their major food source. kind of odd, but look around if you got aphids around in your grow, some produce a sugary excrements which attracts bees too.