Polk had made a deal with A-On-Ie-Mokia Demar, the demon lord of memory, to relay a message to any protege of his that attempted to contact him after his death.
Polk had hidden his box of secrets under one of the giant stones that make up the magic circle, which Lucien and Percival dug up before they learned magic from him.
Polk had apparently set a trap for Percival and Lucien so that we would remain hidden, but we chose to do nothing with the memory trap at the asylum.