I was at a place where they have those black (or are they blue?) lights that provide a glow-in-the-dark experience. You know, your sneakers, t-shirt and teeth all glow. Anyway, I happened to have my iPhone 4 out in this lighting and noticed something on the middle of the screen. The phone was in darkened, locked mode and there was what looked to be a fairly nicely shaped rectangular smudge in the middle of the screen. However, no amount of thumbing over it or wiping it did any good to smear the smudge around or make it go away. So I am wondering what that is? Someone else who saw it just threw out a guess about it being part of the refractive index of the lens or something. But it didn't cover the whole screen, and it seemed to be directly in the middle of the screen. I would say a 1.5" x 1" rectangle. I came home and used some iKlear and wiped down the screen, but I have no way to test it in a glow-in-the-dark setting. Any thoughts on what this could be?