This also tends to happen when smoking in the car but like markem mentioned rotating tends to fix it in this scenario. In your case it just seems like it may have been a poor roll. It happens, it's a product made completely by hand. May have been the last stick the roller had left on a Friday afternoon.
Sometimes my sticks that sit on top in a shelf in my cabinet will sometimes do this as I rarely rotate my sticks in the cab. I think the tops may be more moist than the bottoms resting on the sticks below it. I could also just be nuts! HA!
Did you try touching it up at all or did you just try and see if it ould correct itself on it's own?