Not ready to tell my work friends about our loss this week

We just lost our first baby this week. I was almost 13 weeks and telling people the good news at work. We have a large dinner event tonight that we both aren't feeling up to attending. It's with all of my work friends who think I'm still pregnant and I can't have them bringing it up. I don't know what kind of excuse to give for us not being there tonight. I can't just not show up, or I will be getting text messages like "where are you guys???" Saying I'm sick is a cop out. I can't tell them I had surgery either without questions. Any suggestions? I'm completely broken and unable to function.