I need to get my 3GS replaced. Often, when autofocus is focusing, it'll click and the picture will glitch for a moment. I also noticed that at the bottom of my iPhone, there is a screw missing somehow! I never unscrewed any of the screws ever, and I am the only owner. Should I order the screws somewhere online just in case the people at the Genius Bar see it and think I tampered with things? Thanks.