According to Osho, when the mind truly becomes empty, there is no 'you' left to feel or observe anything - the emptiness itself is the mystery, and you are it. If you can sense 'emptiness' or 'no mystery,' the ego still remains as an observer. Real mystery is ordinary existence, nothing special; drop even the idea of emptiness and simply be.
If you still notice emptiness, you’re still there; when the ‘you’ disappears, what’s left—plain, ordinary life—is the real mystery.