I just assumed it fell off the first time. After that time, I made sure to secure by tapping down with a block & rubber mallet. I couldn't make it budge, and that was just a few months ago. It would take deliberate, strong force to get the bezel off. Assuming it did vibrate off, the bulb still rotated by itself in the socket. Before the missing chrome, functioning turn lights. After missing chrome, flipped bulb. Aliens perhaps? Don't know, but I do know I need a new bezel.