When you cast your first spell each turn it will trigger Vial Smasher the Fierce. If it's also cast from your hand, it will also trigger Possibility Storm. Spells cast from Possibility Storm will never be the first spell you cast in a turn, as it requires casting a spell to trigger. If your spell triggers both, you choose the order the triggers go on the stack, and they resolve first in last out order. If the spell is no longer on the stack when Vial Smasher the Fierce's ability resolves (because Possibility Storm's ability resolved first putting it back into your library), the ability will still remember the cost of the spell you cast.