This sounds like a ponzi scheme.Only early participants get any profit from ponzi scams.I refuse to believe that bitcoin is such type of scam.Anyway,the "lost bitcoins" topic has been discussed so many times on this forum.I don't want to comment on this clickbait Forbes article.2.7M to 4M bitcoins is far away from the truth.
Imagine someone having lots of btc in some wallet and forgetting it's password and not saving the private key.Really?People aren's that stupid