Watching the seventh season, so I might be missing something, but I feel like the only way the hidden world within অতিপ্রাকৃতিক remains unnoticed is because the world is populated দ্বারা idiots.
I mean, the Winchesters have been caught on camera time and time again on the news, when a Doppleganger অথবা Leviathan is posing as them committing murder. While the tape of the first “Ghostfacers” episode containing them is destroyed before it can be spread to the public, the Ghostfacers are shown to have mentioned them in their web series during that one episode where Zachariah makes Dean and Sam forget...
The crew of অতিপ্রাকৃতিক loves to echo past events using imagery and dialogue, sometimes obvious, sometimes subtle. They're mile markers along the journey that encourage the audience to look back and see how far the প্রদর্শনী has come. Here's a few that I've noticed;
Pilot: The obvious mirror image of Mary and Jess both pinned to the ceiling.
Pilot: John hands baby Sammy to Dean and says "Take your brother outside as fast as আপনি can. Don't look back."
Home: Sam says to Sari "Take your brother outside as fast as আপনি can and don't look back." [both events happened in the same house]