A few months ago, I was performing some LST work on a plant of mine and I snapped it's main cola. Beautiful thing about cannabis is that it doesn't take long to heal. I support the plant on a stake, and in about three days, the plant healed up. I should also add that I have broken entire branches off of my plants, but tied them back in place with a rubber band. Healed perfectly.
So, not all is lost.