You are missing the point. The author acknowledges that there may be particles that we haven't yet discovered, but even if there were, we can prove that they wouldn't impact everyday live. In other words, "we know what we don't know".
I gave a true historical analogy of how that could not be the case, I gave a hypothetical example of how that could not be the case, and I gave a quote of someone thinking physics was basically solved right before a massive change in our basic understanding of physics.
It's easy to imagine that there is something analogous to radio waves, that are all around us, but we are unable to detect them with current technology (dark matter might be one possibility).
The point is that even if there were some yet undiscovered particles or forces, they wouldn't have any effect whatsoever on the world around us. This we can say with certainty. Even if it turns out that our current understanding of QM or GR are just approximations of the real laws of physics, again, this won't matter, much as GR doesn't matter at the speed of a moving car and thus you wouldn't take time dilation into account when you calculate the time you need to get from point A to point B.
Would you also assert that radio waves have no effect whatsoever on the world around us?
However, their existence was undetected 150 years ago. Similarly, there are likely things that are undetected by us that also will become very important once they are discovered.