So your saying that because there is no evidence of others being there is proof that they really are there?
Not really. I'm saying that just because we haven't been introduced, doesn't mean we don't have neighbors.
When European explorers first landed on Easter Island, the natives thought they were the only humans on earth. Same parallel. Just because we don't have the means to achieve interstellar travel, and no explorers have made their presence known, doesn't mean that we're all alone in the universe.
It comes down to simple logic. The fact that life arose on this one planet argues for the fact that it's possible for it to arise on others. Given the unfathomable vastness of the universe, and the nearly incalculable numbers of stars and planetary systems out there, it's a virtual certainty that life is common and abundant throughout the universe.
It's just that the distances between life bearing planets are unthinkably large. Only civilizations that have mastered faster-than-light-speed travel, even have a chance of finding intelligent life beyond their own solar systems. We're a long way from having such technology, but we'll get there. When we do, we're going to meet the neighbors.