I think either you or I need to word clear the meaning of the word 'exist'.
If you can't measure it, you can't detect it. If you can't detect it, in what sense does it exist?
This does indeed go directly to the heart of the problem. How does one distinguish between - on the one hand, an entity which has no mass, no energy and no location in time or space, and on the other - nothing at all.
Well, the one has consciousness and awareness etc etc. The other does not.