He whose name was Zaphnath-paaneah could not but know. Joseph did indeed know well their guilt concerning himself, and therefore the question was pointed: what deed is this for which GOD hath visited you?
Related Commentaries of Genesis 44:14
Genesis 44:14-15
14 And Judah and his brethren came to Joseph's house; for he was yet there: and they fell before him on the ground.
15 And Joseph said unto them, What deed is this that ye have done? wot ye not that such a man as I can certainly divine?