Agreed again: but sadly, no convincing evidence exists to support that scenario. Time and distance are great barriers to any supposed contact.
I disagree that we have "probably" been visited.
I do agree that there is almost certainly life elsewhere in the universe, even limiting it to our visible universe. It's a big place. Heck, I'd probably go so far as to say it is likely to exist elsewhere in our galaxy.
But why would that mean that we have "probably" been visited - I.e. More likely than not?
I do agree that time and distance are great barriers to such a visit:
If we restrict travel to light-speed then we have only been broadcasting artificially for the best part of 100 years or so, so that would limit the range of any species detecting us and visiting us today at c.50 light years distant maximum.
But galaxy is some 100,000 light-years in diameter, so to the vast majority of our galaxy we are simply another planet orbiting another star. So limiting travel to c would suggest that even if life does exist, we are extremely unlikely to have been visited.
Assuming that life
is within that range (and we have det cited nothing to suggest that it is the case) it would then require the species to be willing to travel that distance, if indeed it could even achieve close to c.
If they could travel faster than light-speed somehow... then this would push the radius of us becoming an interesting target to 100 light years... Still not exactly a massive sphere. To anything outside that range, we are still an uninteresting ball of rock rotating around an uninteresting ball of gas.
And that is if they got to us today.
The first major event, Roswell, was only some 20 years after em transmissions were strong enough to be detected outside our atmosphere, unless of course they just happened to be nearby at the time.
Now, once our inquisitive aliens get to us, would they really exhibit the behaviour associated with the countless phenomena ascribed to them? They transmit no em waves in our orbit that we can detect. We've detected no artificial em from anywhere but our own planet, certainly nothing in our solar-system (so no craft-to-craft comms), we detect nothing visibly other than a few anecdotal anomalies that suggests rather reckless behaviour of otherwise highly intelligent sentient creatures when buzzing around our atmosphere. Do we only attract joyriders? The jocks of the ET community?
I would say it is possible, but highly unlikely, that we have been visited.
Certainly not "probable".
But as a self-confessed sci-if geek I would genuinely love it to be true.