We wouldn't know. We do know that perceptual errors, emotional disturbances, and the rest are possible.
You are simply saying that we cannot disprove God, that absence of evidence is not conclusive evidence of absence. Sure. But so what? We can go down an enormously -- actually uncountably infinite -- list of propositions for which we have no evidence. If we are sane, we do not grab arbitrary entries from this list and promote them to plausible beliefs, no matter how pretty a story they make.
Your argument is, of course, ancient and has a name. You are arguing for a God of the Gaps. As human knowledge has expanded, thing after thing that was attributed to God in ancient scripture has been shown to have natural causes. Furthermore, "natural causes" have been shown to have a rigorous, inviolable consistency so much so that when we look hard for cases where our existing laws fail, or where there are still pernicious inconsistencies that suggest that they are not quite right and will require future revision.
Since all of the "easy" gaps have been plugged, you are stuck following this chain:
Laws of Nature (microscopic nuclear + E&M and QFT) -> nuclei and nucleons
Laws of Nature (E&M/QED) -> atoms and molecules (Chemistry!)
Chemistry -> Inorganic and Organic chemistry
Organic chemistry + classical E&M and mechanics -> biochemistry and biophysics
Biochemistry and biophysics -> evolutionary biochemistry, neurophysiology etc (Biology)
Biology -> neuropsychology, anthropology, medicine, (Psychology!)
Psychology & information theory & mathematics -> Intelligence and cognition, Artificial intelligence, etc.
At this point, you take the fact that the science is incomplete to extend the quite correct observation that we don't understand all aspects of human consciousness (yet!) in full detail as a "gap" in which you can insert God. Consciousness is only possible with God, God can communicate with humans by directly manipulating microscopic physics, chemistry, biology, psychology laws in ways that directly violate the second law of thermodynamics, and so on. Forget whether or not there is any good reason to think that this is true. Forget the fact that we have an entire, consistent, empirically validated chain of physical law and reasoning stretching from the microscopic to the macroscopic. If you hear voices in your head, it could be God instead of (for example) your right brain talking to your left brain or some other perfectly natural thing. Hence in your mind, there is a reason to believe, and furthermore to invent a whole new "logic" to explain the fact that your conclusions can be held independent of the mere common sense that leads to the development of consistent science.
Obviously -- seriously -- you are mistaken. What you are doing is called the "Mind Projection Fallacy". To quote wikipedia:
Once one has grasped the idea, one sees the Mind Projection Fallacy everywhere; what we have been taught as deep wisdom, is stripped of its pretensions and seen to be instead a foolish non sequitur. The error occurs in two complementary forms, which we might indicate thus: (A) (My own imagination) (Real property of Nature), [or] (B) (My own ignorance) (Nature is indeterminate)
Welcome to B, with an admixture of A. Our ignorance is not an excuse for assuming that Nature is indeterminate and there is room for e.g. violations of the first or second laws of thermodynamics at the whim of a Deity, and your imagination of God filling the gaps in our knowledge is neither evidence nor (worse!) certainty that that which you imagine is a real thing.