37 CFR 4.5: Notice by publication.

If the copy of the complaint that is mailed to the invention promoter is returned undelivered, then the USPTO will primarily publish a Notice of Complaint Received on the USPTO's Internet home page at http://www.uspto.gov. Only where the USPTO's Web site is unavailable for publication will the USPTO publish the Notice of Complaint in the Official Gazette and/or the Federal Register. The invention promoter will be given 30 days from such notice to submit a reply to the Notice of Complaint. If the USPTO does not receive a reply from the invention promoter within 30 days, the complaint alone will become publicly available.