Ideas are everywhere.
Most people step over them without noticing. On the one hand, when you're writing a story, the only thing that matters is the story. As far as I'm concerned, the Cottingley fairy photographs were fakes, but the fairies themselves were real. Lee Harvey Oswald acted alone, but he was aiming at John Connally. Those are human footprints mixed in with dinosaur tracks in that creek in Glen Rose, but they were left by time travellers from the distant future.