The Vanishing Vault.

While stopping at the Bronzegilt Hotel, Slick and Slim, two high-class and well-dressed burglars, overhear Baroness Vodka tell the manager she wishes to place her million-dollar box of jewels in the hotel vault, which is set into the wall at the end of the hallway. The manager accordingly escorts her to the big safe, and she watches him place the little box inside. Next morning the manager goes to cash a check for the Baroness, and finds the whole vault has completely vanished.