Answer to "Why does my mute button not work?"The mute switch with the red dot on it actually sits on top of another switch which is located on the headphone jack assembly (this part comes built into the assembly), the mute switch simply toggles this switch. Essentially it's a piece of plastic with no other gadgetry attached/built into it. If the mute switch has 'fallen off', I imagine that it's cracked/broken off because there's no way it can fit through the whole in the casing if it was still in one piece. A replacement is v cheap, but the fitting of it isn't that easy, if you following the headphone jack assembly guide on this site it should sort you out (patience required).