Raphael Kaufman — Actually, that is not completely accurate according to Halacha. Revealing a confidence is considered avak rechilus, and any information that could reasonably be assumed to be private or secret should be considered as such unless the person told you the information in public (in front of 3 people), in which case it would be safe to assume it is not intended to be secret.
From the “Chofetz Chaim: A Lesson a Day”, Day 136:
“The most severe form of avak rechilus involves statements that reveal information which one was told in confidence. . . Divulging secrets breeds a lack of self control in speech-related matters which leads to actual rechilus. When publicizing a secret could prove damaging, doing so would constitute speaking both avak rechilus and actual loshon hora. Even when no damage was foreseen, the mere violation of confidentiality renders one a “holech rachil.”
Bas Yisroel — Nothing you can do at this point except apologize to the one who told you.