Take a small sharp knife out of your pocket, and cut a button from your shirt.
Pull a few other coloured buttons from your pocket, and ask a spectator to pick a colour. Place the button that the spectator chose in a piece of flash paper.
Set the small package on fire, and its all gone in a flash.
The colored button instantly re-appears on your shirt. It is sewed on your shirt, and can be fully examined. There is nothing to hide!
And what gets even better, is that it takes less than 5 seconds to reset!