Yes, it is. Absence of evidence isn't proof of absence, but it is evidence of it.
This is basic statistics: the larger your sample size, the higher your degree of confidence that your sample reflects the population from which it is drawn.
Simplified example: say you have an opaque bag full of marbles. Initially, you know nothing about the marbles inside, so you pull them out one at a time; they're all blue. Over and over again, all blue.
Can you ever be 100% certain that there's not 1 red marble at the bottom of the bag? No, not until you look at every single marble. However, every marble you draw allows you to be more and more confident that your all-blue sample reflects the bag as a whole.
In a similar way, the more we look for God and don't find evidence of him, the more and more confident we can be in saying that God probably doesn't exist.
I'm not sure how you can come to that conclusion. Logical consistency isn't a guarantee of truthfulness, but it is a requirement for it. If agnosticism is less logical than atheism, then I'm not sure how you can say that it's the "most true".