Just to add to the above, why should we assume that aliens would even want to bother with us even if they were fully aware of us?
There could be millions of alien species out there that have found our planet, but just have no interest. They could have maybe observed us, maybe taken pictures, maybe even learned a little about us, but overall found us not interesting enough for their time.

How many people bother to get to know the ants living in their backyards? ;-)
The only attention we ever give our anthills is to regularly poison them to get rid of them. If they weren't a nuisance, most of us would barely even care enough to notice them. Sure there are those who study ants, but half or more of them are entomologists working on better poisons. ;-)

Anyway, life in the universe could be so widespread that aliens have their choice of who to study and mingle with and who to ignore. Could be we're just a bunch of uninteresting ants to them. ;-)

...