The Midrash (Bamidbar Rabba 11:3) says that the future Redeemer will be revealed, then concealed, then revealed again. This is quoted by the Chatam Sofer on the Torah at the end of the Torah portion of Exodus. He writes: "This is a great test that the Redeemer [Moshe] is concealed...and so it will be at the time of our righteous Moshiach; he will be concealed after his revelation, as mentioned in the Midrash."
(L'CHAIM)