I think there is a good chance you killed them. Bamboo can sometimes re-leaf, but if the culms (stalks) are also brown, they're dead. There is some small chance that part of the root mass is still alive, and you can only find out by watering it and keeping the soil moist for the next several months to see if you get any new shoots coming up. However, even if you get new growth, it may be pretty small in height, and, from your description, I'm skeptical that you'll have success. It might be easier to buy new ones and figure out a plan to keep them adequately watered in the future.