I have an outside hot/cold faucet made by having two ball valves tied together at their exits to form one hose bib. The ball valves are exposed to the elements. These are commercial brass type valves (1/2"). Last nite here in atlanta temps got down to 25 deg. I did not turn water off to either line (hot or cold). This morning the cold turned on and worked fine. The hot handle would turn but no water. I thought the line had frozen, but it appears the valve has failed in the "closed position". The handle and stem going to the ball turns but the ball doesn't turn the valve to allow water to come out. How could the stem separate from the ball? Why didn't it happen to the other side if the cold temp was the cause? thanks