In Sight of Memory: The Legend of the Lost Colony

Lotus had everything: a breathable atmosphere, a vibrant ocean ecology, minerals. It was ideal, until the colonists discovered that they were losing their memories. Even as language slipped away from them, as their fingers unwittingly traced letters and images, the people of Shiptown hastily reengineered their literate, technological society into medieval ignorance. A few generations later, with most of the population shambling like beasts, the villages along the river Lethe are connected by the coin cult and faded legends of their former glory while only those in Shiptown recall their interstellar travels.
The collector guild fights to keep the coin cult intact and maintain order, and the lethargic settlers are contented until Blier is found raving about a lost colony. In a reveal that threatens their entire way of life, this unmemoried collector's tortuous journey from forgetfulness back to The Perdu uncovers the long-buried secret of their past. Follow Blier and Linder as they struggle through a world of farming villages and political dogma to Shiptown where they hope to trace his chaotic thoughts to The Perdu.
In a race against time, with the mindless beasts of his gnawing memories clawing back into consciousness, Blier's trek across a desiccated landscape transforms both himself and his world. Linder wants to save her new love, Katir wants her father back, and the collector guild is desperate to understand why Blier hates the coin cult and yet clings fanatically to meaningless trinkets: a child's toy, a knife, and an unusual arrow.