The Baalei Tosfos Would Never Think That Way

Once, Rav Chaim was sitting at a gathering of Torah scholars and shared a Torah thought. One of the audience argued that a certain Tosafos said something that seemed to argue against what Rav Chaim had said. Rav Chaim responded: “Tosafos do not say such a thing.” The relevant blatt Gemara was opened and validated Rav Chaim's shita. After a moment he remarked, “Do you all think that I am fluent in every single Tosafos, even knowing what isn't written? No. But I understand that it would be impossible for Tosafos to say what he claimed they say.”

(Ishim Veshitos pages 33 - 35 as told by Rav Meir Berlin)