Borrow a small object from the spectator, tie it to a playing card with a rubber band. In the blink of an eye that same object can visually vanish.
With the object tied down in this way it looks impossible for that object to move anywhere.
Hostage is a innocent looking gimmick that allows you to vanish various objects openly. It's fun to build and practical to use. You can easily perform it as a stand-alone effect or a part your repertoire.