In "Titanic Halifax," (available through Amazon.com) by Alan Jeffers and Rob Gordon, they say, with pictures of Mr. and Mrs.:
"The family of Philadelphia millionaire George Widener came to Halifax to claim his body when the 'Mackay Bennett' returned. The body was not found."
The body of George Widener's valet, Edwin Keeping was recovered after the sinking. From what I've heard, papers belonging to Widener were found on the body and thus for a time he was thought to be Mr. Widener himself.