Someone would have to be very close (30 light years or so) to have noticed us and have time to signal back. Even among those, likely they would just watch us and then decide if they want to chance contacting a race that has thrown nukes at each other.
To put that in perspective there are about 400 stars within 30 light years of earth and among those stars we have found 26 exoplanets. This radius represents only about 0.00014% of just our own galaxy and an infinitesimaly small portion of the entire universe.
And if that is accurate, then essentially we ARE alone in the universe. There simply isn't anything close enough - we'll be enveloped by the sun or some other catastrophe before that happens.
