Another thought. Was it windy? Wind across the smoke vent seems to really suck the heat right out of a Bradley. Protecting the vent from the wind helps a lot when you are smoking in windy conditions.
If your area is often pretty windy, like mine is, a short section of stove pipe and a vent cap might help reduce the vacuum created by wind across the vent. (Note, I have removed the vent damper from my smoker to prevent additional closed vent accidents. This made it easy to semi-permanently attach the stove pipe to the vent by cutting some tabs on the end of the stove pipe and bending the tabs through the openings in the smoke vent.