Dawn Mello — the former creative director of Gucci who hired Tom Ford and who helped make the careers of Donna Karan, Michael Kors and Frederic Fekkai — is recovering at home with a shattered femur after being run down by a bicycle messenger on 57th Street. Mello, who was also president of Bergdorf Goodman, has been laid up for more than a month. The cyclist fled the scene and has yet to be found. Mello declined to comment, but a source told us a private investigator has been hired to track down the culprit.