Tanis slipped, landing on his hands and knees at the bottom of the pot where he discovered that the stone draconian had decayed into dust, allowing him to retrieve his dagger.
4e doesn’t have a Disarm action, probably because no one managed to figure out how someone could be “disarmed (save ends)” or “disarmed until the end of their next turn”. Taking someone’s weapon either handicaps them for the whole fight (for most weapon users) or has no effect (for most monsters). This kind of swing is not for 4e.
Draconians could actually be a great addition to 4e, for those DMs who want to (temporarily) frustrate their sword-swingers. In Dragons of Autumn Twilight, draconians turn to stone when killed, trapping melee weapons… but after a few seconds (six? twelve? save ends?) they crumble to dust, freeing the weapon.
A handful of draconian minions might make for a fun 4e fight, if you don’t mind frustrating the melee characters while allowing the casters and ranged characters to get off scot-free.