For what reason does the narrator get particularly nervous when the Memory Police are searching her writing desk?

During the Memory Police's search of the narrator's house in Chapter 17, the narrator becomes particularly anxious as an officer searches the drawers of her desk. It is not the contents of the drawers that is worrying her, however. Instead, she is frightened that the Memory Police will look behind her dictionary, where she keeps the funnel system she uses to talk to R.