Determine if the button is above or below the hole.
If it is above the hole, push the button down until it snaps into hole.
If it is below the hole, take a large paper clip or any other strong wire and straighten it out.
Form a small loop at one end.
Slide the paper clip into the tube past the button. Slowly with draw the paper clip to hook onto the button.
Continue to pull the button up until the button snaps into the hole.