I believe I have a frozen pipe in my master bath. The water in the whole house runs fine... and even the cold water to the master bath sink works. It is only the hot water tap in the sink that doesn't work... not even a trickle. I've tried a bliw dryer but the pipe goes into the wall - an outside wall - and nothing seems to help. Ideas? Do I need to panic and call a plumber at midnight? Or just open the cabinet door, leave the taps open a bit, close the bathroom door, crank the heat, and hope for the best?