I won't comment on the debunking. I am sure there's a logical explanation but I am not qualified to make decisions using the evidence I have (which is often true of people on both sides of the discussion, here, generally).
I terms of "are they here", it isn't totally crazy to imagine an AI that can self replicate it's frame, and use this ability to explore the galaxy. When it finds places of interest or that are particularly useful for replication it might hang around.
I'm do not think that is what is going on but it is certainly a possibility. Very remote, of course.