Users can 'unarchive' documents that are archived in error by clicking the unarchive button at the end of the list row. Navigate to the Archive section to see archived cases.
When unarchiving, you'll need to select a status to revert the case to. Once unarchived, you can find the Cases based on the status you assigned it to.
If you accidentally deleted a transmission, your Site Administrator can find and un-archive it in the Transmission Archive section (Alt +A).