Do I have a right to be upset with partner?

So me and my partner were supposed to be going to his friends birthday party last night at 6pm, he called me at 5 and told me he was still working and won't be finished until 7ish so he will just go for 1 drink and to give his friend his present. It is now 8.15am the next morning and I still haven't heard anything! I am 18 weeks pregnant and we already have a 6year old that I had scheduled a sitter for. My partners brother was also at the party so I text him to get him to get my partner to call me and my partners brother is now saying I have no right to be upset and angry that he was at a party,what did I want him to do. I don't mind him going out, but to ignore my calls and texts and not come home I think is more upsetting.