Q reappears in McGonagall's back garden. He has a largish box with him. He's using a hover charm on it because it's quite heavy. "Severus!" he calls as he re-enters the kitchen. "It's me! I'm back! And whoever said you can't always get what you want didn't reckon with me!" He's maneuvering the box rather carefully through the door to the living room. It rattles and clinks as the contents bump against each other.
He's far enough away and they're concentrating so Sirius won't have heard the name. ;)