Halloween five-second rule

The scene: Isaac and friend have stopped for a [second] ‘candy-break’ while trick-or-treating.  Isaac opens a candy bar wrapper, and the candy falls in the grass.

Richard: “Grab it!  That’s still good.”
Isaac [picking up candy]: “Are you sure?” [examines candy]
Richard: “Sure.  Five-second rule!”
Isaac [carefully eyeing candy]: “Well, okay.”
[Isaac bites candy bar in half, chews]
Richard: “I saw a dog pee right here this morning . . . . “
Isaac: [pauses, eats second half of candy bar].