In the previous episode, Treasure of John Walking Fox (1966), the room keys at the Dodge House are kept in individual cubbyholes on the wall behind the clerk's desk. In this episode, they are on hooks on a little wall by the stairs leading to the rooms. This was probably done to make it easier for David to grab the Pass key.
After Thad lets David out of the cell, he hangs the keys back up on the hook outside the jail area. Later, when Barrett come in looking for Matt, the keys are gone. Matt and Festus are out of town, and Thad hasn't been back to the office.