If you go there now, you will see them.
Travel back in time, to the place you can't get past; come in at a low orbit around this distant world.
Maybe you've been here before. You've watched their security ships rise to escort you, silver dots against the big night, advancing slowly towards you like travelers across an ancient valley.
They will not remember you. You'll play your part like an actor and you will know your lines well. For them, it will be the first time. Always the first time. You will introduce yourself as a visitor from their future - perhaps you are of another race, perhaps one of their own.
They will not welcome you. They will treat you with suspicion, as they would any alien. They're not used to seeing aliens. They want to know what you can offer their settlement. You must bring beads and trinkets: a fusion reactor, a hyperspace drive.
They will not love you. A visitor from the future does not bring them any hope, because it is their past they've lost: their homeworld, their families.
They will not remember you. After you have gone, returned to your universe and its comforts, they will remain behind. They don't want your world. They will keep your treasures and your technology. But they'll forget your face and your name.
You do not belong to Darkhaven.