Home button not working after getting wet

I phone 3gs got a little wet and now the home button does not function. Phone has been sitting for awhile and im positive its dried out (4mnths). I took apart another working iphone 3gs and put its screen(including home button)in the broken one and still no response(and vice versa the working phone worked with old screen/HB). So im positive its not the actual home button. so im at a standstill till i can figure out what else it could be, Ive hear that the dock,dock conn. or the dock houseing could be the issue but how to you know which it is? Any thoughts?

Thanks!