There was no good way to respond to George at that moment, but he settled for raising his middle finger in farewell as he continued to walk to the fireplace. "And I'll be thinking of you the whole time!"
Pinching a bit of Floo powder in between his forefinger and thumb, he flung it into the fireplace and watched the flames spring up. Stepping into the flames, he disappeared before George decided he would throw the quill back at him.