the power button fell off on my first bumper black/transparent today
If you still have both pieces, you can re-attach the power button to the attachment piece with a small dab of crazy glue. This should fix and keep the button in place. I am pretty sure the glue that is being used on these is really weak or not enough. The power button holding down the phone button is also a big problem being worked on.
sw-box and other factories/sellers are aware of all the button issues and will be resolving them.