This is the best analogy I've heard. We've only been able to meaningfully look for less than a hundred years, our capabilities for looking are very limited, we haven't even looked everywhere we can look, and this is all assuming that our technology can even detect it. It's even possible that it exists under our noses, but is undetectable to us for the time being (like underneath ice sheets on Europa, or something like that).

Anyone saying the search for life is "over" is painfully unaware that the search for life is just getting started assuming humanity makes it through the next century.