No one had been allowed to enter the Lord Voldemort's quarters in the castle for weeks. That should have been another large clue to anyone too thick to understand that something serious was happening. He despised weakness and strove to make certain that no one ever saw him the least bit vulnerable or human. Half of his influence was in the fact that he could terrify his people with just the threat of unimaginable power. Seeing in his place a feeble and sick man would have ruined the illusion. That would not have been allowed.