Well, in this case, the signed paper is never actually delivered to the other party, and the other party has no knowledge that you ever signed it in the first p

Well, in this case, the signed paper is never actually delivered to the other party, and the other party has no knowledge that you ever signed it in the first place. A signed piece of paper is neither necessary nor sufficient to form a contract. It's prima facie evidence that an agreement took place, but that's not the same thing.