are you sure you actually picked the trait? the level up screen has a weird way of displaying selected and suggested traits. also, is this the default fireball spell from fire III or the fireball buff (anointed by fire or something, from the mgic techtree)? not sure if the trait works with that buff (never tried it). if you also have life IV, you get wellspring, or at water III you get pandemomium. those should also be instant cast with the trait.
