Was I Wrong To Lie About Seeing My Ex?

So my ex-wife and I have been divorced for months now but still run into each other occasionally at social events. Recently she had a date with someone new, and I saw them together from my balcony one night around 9 PM. Didn't say anything to her about it though, just told everyone we ran into her by chance the next day like nothing happened. Was it wrong of me to keep that little secret?