Baso said nothing to that last remark by Nangaku, something that we should not idly overlook. There was his casting aside the tile to catch a jewel: he was turning his head and changing his expression (symbolizing normal behavior). Further, nothing and no one can rob him of his making no response.
Zen Master Joshu once said, "Tonight, I have given the answer. Anyone who understands the question should come forward." A monk stepped forward and prostrated. The Master says, "Just before I threw away a tile to pull in a jewel, but instead I have drawn out a lump of clay."
(adapted from Shobogenzo Zazenshin by Zen Master Dogen, 1242)