Obviously it was "detected" -- it was caught on camera! And if a news camera can see it, so can more sophisticated things.
You're apparently hoping for a worst-case scenario, such as Chinese provocation, so that's what you see.
But really ... the more plausible explanation is a US test using US assets, and they're just not going to tell you what it is. They're the ones with all the info, and they have no need to tell us what they actually know.
Meh..you’re going about it all wrong. Nothing bad or mysterious happens on this planet that can’t be blamed on 1) illegals, 2) moose limbs, or 3) chicoms...since the first 2 can easily be ruled out, it HAS to be the Chinese! /s