The probability that other life exists somewhere in the vast universe is greater than 0. Math alone makes it so that we have every reason to assume there's some life somewhere.
That said, the opposite is true of first contact having been already made. If we had contacted alien life, there would be no way to hide it. Numerous scientific labs around the world, from NASA to SETI and beyond, would have noticed, and they wouldn't have kept their mouths shut. Even amateur star watchers would have found out. Any people who put enough time, money, and effort into traveling across galaxies to find us would have made it clearly known, and if they had been kidnapped by dæ gubernmint, there would be an intergalactic conflict as a result, if not a full-scale war.