At the beginning of Act V, how does Shaw let us know where Eliza is?

Mrs. Higgins is in her drawing room when her parlor-maid enters and informs her that Pickering and Higgins are downstairs calling the police. Higgins enters and explains that he is frantic that Eliza has left-he cannot find anything and now has nobody to remind him of his appointments. Mrs. Higgins scolds her son for calling the police as if Eliza were a lost parcel.