Postal workers in Spokane, Washington, on Saturday retrieved a wayward letter suspected of containing the deadly poison ricin that vanished for several weeks after it was sent from Washington state to a CIA address that does not receive mail, the FBI said.The envelope resembled four ricin-laced letters postmarked May 13 from Spokane that had addresses penned in red ink, FBI agent Frank Harrill, an agency spokesman, said in a statement.Matthew Ryan Buquet, 38, of Spokane was charged last month with mailing a threatening communication in connection with one of those four letters, which was sent to a federal judge but intercepted by a court employee during a screening process.