In the scale of time it is pretty small. Yea there is a slight possibility something visited us or watched us once, but I doubt it. Of course there is other life out there. Out of the billions and billions of galaxies, you think our solar system is the only one that happens to have life on it? Of course theres gonna be things more advanced than us, alot of things more primitive than us,

maybe the reason we don't know is because this little solar system hasn't had anything special on it, maybe when we are more advanced something may be more interested in communicating with us, maybe some things have seen us, I mean SETI has been sending out signals, im guessing something out there would be able to detect it, maybe nothing is just close enough to detect it. More likely is nothing out there is interested enough to pay for and focus on exploring, especially when they know how endless the universe is.

It's like the depths of the ocean. It's unknown what exactly is down there, not alot of people have gone and checked it out, alot is undiscovered and there's alot of lifeforms down there we don't know about, but we know there's most likely nothing of any use or importance and there's lots more important things going on to care about.