I'll just add my 2 cents that whereas I am 100% cast iron certain that aliens have never visited Earth previously, I am absolutely NOT cast iron certain that they might not do so in the future, possibly even the near future.
One of the reasons I am certain they have never visited is that (sorry if you've heard this from me before) no Alien species has any clue we are here. Why? Because until we started emitting radio waves, they would have no idea that Earth is anything other than a rather boring planet orbiting a rather boring sun in a rather boring region of a rather boring galaxy. And with so many countless trillions of trillions of planets, then why on earth should they invest the energy, time and effort of journeying for light years to visit a very boring rock? They wouldn't - it makes no sense.
And since we have only been emitting radio waves for 115 years, and since radio waves "only" travel at the speed of light, only those planets less than 115 light years away, could possibly know we are here. An alien race 116 years away, don't "see" anything when they look at Earth. It looks silent, dead, with no signs of intelligent life and no reason to take any interest in it. They see Earth as it was in 1905, the year before the first radio broadcasts. Which means it looks to them like every other boring planet. Until next year, when the 116 light year away aliens, will see the Earth spring into life. And in another year, add in the 117 light year systems. So every moment that goes by, more and more planets in systems near us will see that there is intelligent life on Earth, and suddenly, we become very interesting to them indeed.
The reality is 115 light years away is bugger all. What this means is that we are currently invisible to 99.9998% of the potentially intelligent-life harbouring planets in the milky way. If intelligent aliens are out there, they have no idea we are here. Yet.