Lost Starships

Even with an FTL drive, it would be easy for interstellar spaceships and even for entire extrasolar colonies to become isolated both from each other and from mainstream galactic civilization, if there were any. In Poul Anderson's Psychotechnic History:

the Traveler, thrown off course by a trepidation vortex, founds a colony on Harbor, then initiates the Nomad culture;

the New Hope, thrown off course by a trepidation vortex, founds a colony on Atlantis that remains isolated for three hundred years;

the crew of another Star Ship is stranded on an inhabited planet for an indefinite period and I am about to reread "Star Ship," in Starship, about this third scenario.

"Gypsy," about the Traveler, and "Star Ship" are set between the invention of the hyperdrive in 2784 and the founding of the Stellar Union with its Coordination Service in 2900 whereas Virgin Planet, about the discovery of the Atlantean colony, is set in 3100 which means that the New Hope was lost about 2800, approximately 15 years before "Gypsy" and 75 before "Star Ship," in the period when FTL travel had just begun and there was as yet no knowledge of trepidation vortices.

The Chronology of the Psychotechnic History should include the loss of the New Hope about 2800 as well as the events of Virgin Planet about 3100. After Virgin Planet, there is a rapid succession of a few stories before the Stellar Union collapses:

3110 "Teucan"
3115 "The Pirate"
3128 The Peregrine
3200 The Third Dark Ages