Dujonian' Hoard by Michael Jan Friedman
There's a bar called "The Captain's Table", where those who have commanded mighty vessels of every shape and era can meet, relax, and share a friendly drink or two with others of their calling. Sometimes a brawl may break out but it's all in the family, more or less. Just remember, the first round of drinks is always paid for with a story... even if you're Jean-Luc Picard.
For more than two hundred years archaeologists and treasure hunters have dreamed of Dujonian's Hoard, a fabled trove of priceless historical artifacts that may contain technology that will shift the galactic balance of power. A dream was all the hoard seemed-- until a former Starfleet officer goes in search of the treasure and turns up missing. Now everyone from Romulans to Cardassians to an enigmatic female starship captain is looking for Richard Brant, including Worf and Captain Picard, who have gone deep undercover on a secret Starfleet mission to rescue Brant, if he's even still alive...