Just because you can't prove that the number of times something has been pirated is equal to the number of would be sales does not mean the person who owns the product doesn't lose out.

Parent-poster is talking about "losing out" in a specific way, where rights-holder copies would temporarily vanish or become unusable for some reason. (Which obviously doesn't happen.)

That's rather different from the definition you're using, where "losing out" is much more expansive, including hypothetical decreases in potential future sales of new copies that haven't yet been manufactured.