Note that the author is saying that he couldn't find any proof that the story is true (e.g. a primary source or corroborating evidence) from his internet searches (Google, Hacker News etc.) But just because something is not on the internet doesn't mean it didn't happen. In this case, the story refers to a military (presumably classified) project from the 1960s (i.e. before the internet), so I wouldn't be too surprised if there was no proof on the internet.
