If someone has a secret like that it would only be a matter of time before 1 someone else does it or 2 people figure out it is known for the very reason that things people shouldn’t know are known or 3 it is leaked.
This is all pretty moot as we know it is a matter of time before generic quantum computers are created/sold. As soon as they are there will be ramp up time to become wide spread, mean while a migration to a new technology that doesn’t use the difficulty to factor large numbers made of two primes as it’s core security. (General Quantum computers crack this using shor’s algorithm)
In short, if someone has this they are their own bottle beck right now and it means the trillions of various encrypted systems are for the most part completely safe. Especially considering the fleeting nature and re-encryption on a message by message nature of so many communications