Could be a vandal just pulled it out. Likely wouldn't take much, kids come up with the weirdest $h!+ to mess with on cars. I've always thought in the back of my head, what if someone cut or tore out that button...for it to be covered under warranty it would have to be obvious manufactures issue. One other thing to note, some parts of the car are not covered by the 60k/5 year. Things like the Nav screen and radio components like speakers and amps, not covered by that warranty, their's ends at 36k/3 years. Most of your cosmetic exterior stuff typically ends at 36k/3 years too, makes me think the button might be in that realm. Extended warranty might cover some of it past a certain point, but that's a different agreement. Point being, don't be supersized by the fine print. But that said, if they dealership comes right out and says there's no way that just fell out on it's own, then you are on your own for repair.