When someone offers us a secret to keep and we promised, it does not mean that when we discover this truth by other means without the bound of such promise, before or after the promise, that our decision to reveal the truth are bound by the same promise. For if that is so, that offer has unwittingly transformed into a command, and one either obeys the command or not, instead of promising to keep it or not. A command requires authority, an offer does not.
For example if someone says: Tim, I have a secret to tell you, you must promise not to tell anyone.
Tim: I WILL MOST DEFINITELY PROMISE that I will not reveal that it is you who has told me as I would treat it like gossip. But as for the truth, no man, not you nor I have enough authority nor power to hide it or speed it, in time, the truth shall always reveal itself, in its own good time.
We must never build our foundation of truth upon gossips.