Questionable Logic

Four minutes ago...
Me: Who got toothpaste on the rug in the bathroom?
J: That's not my toothpaste, mine is a lighter color.
S: That's not mine either, mine is a lighter color too. Mama, I know, we can put more toothpaste on the rug, then we will know whose it is!
Me:
(Yes, that would be dumb-struck silence)
Me: Wow, I never would have thought of that idea.
S leaves all proud of himself. And I am now going to clean up the toothpaste.