This is why I like to get people to -- when there's NOT a crisis on the table - -decide what their dealbreaker is going to be in terms of number of "strikes" on re-contact when two people are supposedly in no-contact.
One, but only if they self-confess? One, even if I have to find it out, but they then "come clean?" Two? Other?
Because once it happens, you're reeling, and it can be hard to think straight, and mistakes can be made in either direction (too lenient, or too strict). When YOU are calm, and in a good place, YOU should determine what YOUR line is. I knew what mine was, and I was really glad that I had "hidden it in my heart," as it were, because it helped me with forgiveness and to give her one more chance (I guess I kinda just said what mine was, lol).