THIS ranks up there, in my book, along with statements like "sail too far and you'll fall off the edge".
Everything need NOT be directly observed to conclude its existance; such was the case for quite awhile with 'matter' and the conclusion it was ultimately composed of unseeable (at the time!) atoms ...
I suppose that either you are sticking with the original definition of matter or you are many, many centuries out of date. The atom, as originally proposed, was an indivisible unit. BTW, we still can't "see" atoms, we can see instrument renderings which may or may not be truly representative of "atoms". We construct instruments based on looking for something we already have a conception of (to prove it true) and should not be surprised to find that they confirm that conception (they're doing what we designed them to do, finding what we designed them to find).