Its in the graveyard scene when Wormtail is performing the spell that brings Voldemort back. First he uses a wand, which he holds in his right hand, then slides the wand into the inside pocket on the left side of his jacket. For the next part of the spell he pulls out a knife with his left hand and cuts off his right hand which drops into the cauldron. For the final part of the spell he needs the wand again, which now mysteriously appears in the inside pocket on the right side of his jacket where he can reach it easily with his left - and only - hand.