False. A recent U.S. decision holds that such a disclosure must be well known to practitioners of the art, not just known to a few! Publication is no longer sufficient.
You do have to lie and say you thought of it independently; something impossible to disprove. The number of people who'd lie for big money is... innumerable.
You can patent ideas thousands of years old - if they're not well known to practitioners.
You're right that any publication will not be sufficient. A publication needs to be discoverable by the practitioners of the relevant art. However, it does not need to be well-known to them, nor does it need to be actually known by any of them. It only needs to be reasonably discoverable.
You do have to lie and say you thought of it independently; something impossible to disprove. The number of people who'd lie for big money is... innumerable.
You can patent ideas thousands of years old - if they're not well known to practitioners.