渺无影踪
      Explanation: Traces and shadows look a little less than
      Usage: Verb-object type; as predicate, adverbial; containing derogatory
      Source: Mao Dun, "Corrosion of November 13": "to recall fond dreams of last night's upside down, but - have been vague and without it anyway."
  • Thesaurus:  Vague and without a trace