they just don't have sensors that can detect things that aren't emitting things at us and are already here

technically, solar plasma is essentially dark matter... we only know it comes after the x-ray burst because that's how it happened many times, we can't measure it, they model it based on many sensors and their models of the emission and the historical results of that

really, dark matter is anything that doesn't emit radiation constantly, and the only way we can detect it is with radar or visual light or something, and those two things just fade off into useless after a few hundred thousand miles, in photography they call that distance "infinity"