A floor call I had never seen

[PantsOnFire]

I am not fully sure what you mean by the dealer "...instead of giving the button his fourth card he dealt it to replace the exposed card."

In any event, if a player has the wrong number of cards and there are two actions after the blinds, the hand is dead in most places I have played in.

However, if the action is still pf and the floor ruled that the player can get the burn card and the exposed card becomes the burn for the flop, I wouldn't complain.