Meh, sure, why not. It's not that much of a stretch to say that another person could've managed to escape in the middle of all the chaos, or otherwise survived for long enough to heal himself through the aid of potions or whatever. Maybe the monsters, assuming that everyone was dead, chased after the sole moving target (AKA: Lily)?
As far as how close the party was; I figured at least Lily only joined just for this thing, although she'd obviously knew who was who. As for how close Kenneth was to the rest, you're free to fill in that yourself.