Yea, I did, what reason is there. What mundane things do they hide? Stuff that is likely directly affecting them as a group. Another civilization's existence would cause media hysteria for a week then just become common knowledge that people would not care about. There is nothing far fetched about life elsewhere, what is far fetched is hundreds of countries hiding this fact for this long. Things people see pretty much always has an explanation.Did you really ask why the government would need to hide the existence of another civilization? They keep secret much more mundane things. Start there.
Also, a civilization that can travel like would be required to visit us, has probably been keeping an eye on us anyway and figured their best chance of visiting or communicating would be through superiors. Kinda like how all of SVTP only deals with a GM or owner when it comes time to buy a car.
Everything is unprecedented until it happens. It's not THAT far fetched in the grand scheme of things.
Just look at the map of our galaxy and how far our radio signals have gone and how so damn incredibly insignificant that distance is. Understanding the sheer volume of space and how insanely slow the speed of information (light) is helps see how damn unlikely it is that we have encountered anyone (yet). One day we'll probably receive a real stray signal from some ancient civilization that fired those signals thousand-millions of years ago, until then they are IMO a theory