So, of COURSE I dropped the screw that you are not supposed to lose. I was being careful, but as I did not want to lose track of it, I attempted to put it back ing the phone FIRST. Bad idea. This makes the plate kind of springy, and my screwdirver slipped, and the screw popped up, spun in the air, fell between my legs, bounced off my padded chair, and clattered around on the floor. I searched for an hour, and could not locate it. BE IT KNOWN, at least in MY CASE, the screw WAS INDEED attracted to my magnet (I keep a powerful round magnet stuck to the shaft of my drivers to provite the magnetism, far more powerful than a regular magnetic screwdriver. This being the case, I WAS able to provide a substitute fron a bag of iphone 4 screws, and my compass calibrated flawlessly upon power-up. YOUR MILEAGE MAY VARY, but I thought I'd add my experience.