Judgment Day and Rebuke

When Yosef reveals himself, he asks his brothers, "Is my father still alive?" Yehuda has just spent the whole conversation talking about their father's life, so what is Yosef really asking? And why does the Midrash Rabbah call the brothers' silence a warning about Yom HaDin?The Beis HaLevi reads it as a rebuke, delivered in a way most of us would never think to try. A mashal about a father who sails off to a faraway place to find riches, and what he carries home, asks us to look at where we put our effort.