"'Proof?'" Russell echoes, squinting at him. "I don't... that's not what I was looking for. But I suppose, when Benjiro, uh, touched it, he got an echo from it. And not an echo about a giant mouse."

There's the mix of avoiding admitting the context in which Benjiro was climbing on it for hours, the confusion of his imperfect recall of details of whether it was the ordinary sort of echo or something different, and so on.