Midrash sobre Zevahim 4:13

And Reuben || went down by night to bring up Joseph out of the pit, but he did not find him there. He said to them: Ye have slain Joseph; "and I, whither shall I go?" (Gen. 37:80). And they told him what they had done, and the ban which they had proclaimed; and Reuben heard of the ban, and was silent; the Holy One, blessed be He, because of the ban, did not tell the matter to Jacob, and (though) concerning Him it is written, "He sheweth his word unto Jacob" (Ps. 147:19); but this word He did not shew unto Jacob, therefore Jacob did not know what had been done to Joseph, and he said: "Joseph is without doubt torn in pieces" (Gen. 37:33).