left me hanging

I slept with someone from work, who's a freelancer, so we barely see each other in the office. It happened the first time a month ago and it never led anywhere until last Friday when we ended up in a party. It was amazing, we had brunch, and texted for 2 days until the week started again and he went radio silence. I haven't seen him since then, and not sure how to behave when I see him in the office again. I feel like a 15 year old girl all over again, and I'm 30!!! This is ridiculous right?