This is due to the strange ability of teaspoons to create themselves instantly from nothing more complex than dirty washing-up water. You finish washing up, swirl your hand around in the bowl and confirm that there's nothing left, yet when you empty the bowl you find another teaspoon has suddenly materialised.
Teaspoons also have the as yet unexplained characteristic of disappearing spontaneously from cutlery drawers. You know you put some in the drawer, but when you need one, there's none there.