My Unexpected Hookup at the Office Party

I recently had a casual date with someone I met online. We both agreed it was just a fun night out and nothing serious. The next day, my company hosted an office party where we have drinks and snacks while mingling. To my surprise, she showed up too! As the alcohol flowed, we got more comfortable around each other. Eventually, we found ourselves alone in a quiet corner of the room. Without saying much, we ended up kissing passionately. It wasn't planned or anything like that; it just happened. We both know it's not serious and shouldn’t lead to anything beyond this moment. But now I’m wondering if this kind of spontaneous thing is common with casual dates turned into office parties? Should I tell anyone at work about us, or should we keep it strictly private?