At about 1930 eastern time, a Piper PA-28R-200 struck trees during a forced landing near Fredericksburg. The pilot and passenger were not injured. The pilot said he was approaching Shannon Airport and decided to switch the fuel from LEFT to RIGHT. The engine quit. Examination of the wreckage revealed the fuel selector was in the OFF position, but it was unknown if the fuel selector was moved by emergency response crews. Additionally, when the fuel selector was moved from LEFT to RIGHT, the selector contacted a sheet metal screw that felt similar to the selector being secured into the RIGHT detent. However, at that point, fuel flow would not have been possible.