Contact your Site Administrator as soon as possible. Site Administrators can 'unarchive' transmissions that are archived in error through the Transmission Archive.
To get to the Transmission Archive by clicking Transmission Archive under Transmissions or pressing Alt + A on your keyboard. Note that you must be a Site Administrator to do this.
Once in the Transmission archive, locate the accidentally archived transmission and click the Unarchive button at the end of the list row.
The transmission will be restored and can be found in Inbound or Transmissions > Fax.