The Diana was a Federation starship that was plundered, sometime prior to 2364, approximately twenty-five light years from where the USS Muleskinner was spacejacked.
In 2364, the location of the Diana was labeled in a star chart. This chart was stored in the USS Enterprise-D library computer. Later that year, the chart was scanned by Outpost 63. (TNG: "The Naked Now", production art; TNG: "The Last Outpost", "Conspiracy")
This starship was only mentioned in writing.
The Enterprise computer's star chart was a drawing by Rick Sternbach that had originally been published, years earlier, in the Star Trek Spaceflight Chronology (p. 95). This chart showed early commercial lanes and exploration routes following the forming of the Federation, but no text attesting to this fact was included in the portion used on screen, just the labeled names of the ship attack locations.
According to the unseen accompanying text, "But the dark side of this expansion was the encountering of space pirates, who increasingly terrorized and destroyed Federation starships. The spacejacking of the ore freighter USS Muleskinner and the destruction of the transport Diana were among the most prominent instances because of their close proximity to major Federation trade routes."