...It might be one of those ancient things developed aeons ago by some civilization that no longer can be contacted for specs. Everybody knows how to build the things now, but nobody really
understands how they work.
For a while, people liked to think that transporters were such a thing. Then it turned out that everybody had them in the 22nd century, and Earth had even developed its own seemingly independently. Even earlier on, people liked to think the same of warp drive, with the same disappointing conclusion... It does seem that amazingly alien and futuristic technologies are invented by lone inventor weirdos, while at the same time supposedly more conventional engineering teams with vastly greater physical and intellectual resources produce much humbler technologies. Which isn't quite as fantastic / scientifictional as these being alien technologies.
Although perhaps this is actually even more fantastic. How do these individuals come up with these impossible ideas, let alone the means to turn them into an industry single-handedly? Is somebody supernatural/fantastic/scientifictional whispering in their ear, introducing the idea and then walking the inventor all the way through to practical execution?