There is no need to pitch any additional yeast. Don't worry about whether you see visible airlock activity -- that means absolutely nothing whatsoever. In all likelihood, CO2 is escaping around the stopper, lid, or somewhere else. Also remember, CO2, like liquid, will follow the path of least resistance. Your krausen is the sign of fermentation. If you doubt it, take a gravity reading. If specific gravity has dropped, you are fine. If not, you'll want to take another reading when your new vial arrives.