Just happened to me. Except it was half hanging off by a part of the gasket which was partly ripped. I just went to use it and it was half out of place. I have no idea how it happened - never banged the camera or anything - just put it in my camera back and then pulled it out again.
'Only' charged me $104 I think, which was parts + tax + shipping. They let me off the labor. I bought the camera last November so it was in warranty - they called the labor charge 'In Warranty Standard Labor Charge'. I guess the fact the gasket was partly ripped indicated that it could have been misuse rather than a manufacturing defect so I was OK with the $100 charge.
They did also clean the viewfinder/mirror and sensor even though the form indicated that was an extra charge. And they did need cleaning, so that was nice.
Just looked at the receipt - said the 'unit requires a new back assy'. So I guess it is more than the toggle + gasket. Or the gasket is one piece over the back. The actual button seemed fine on mine and was still semi-attached.