(Someone suggested that I post this to my post. Thank you!)

Just wanted to post an update for this situation:

I did wait for him to come home and by this time I had mostly cooled off. The first thing he said when I saw him was I'm sorry, which is I was surprised at.

I guess what I had mentioned previously was true. He didn't know it was an employee only event (He told me the flyer had said something about family and he took it as family included as well, but it was really about calling their company a family) and when he got there he saw only they were there. Also, he said he wanted to disuade me by telling me he wasn't going to pick me up and thought I would just go home. He said he didn't want to tell me not to come because he didn't want me to feel like I wasn't welcome with his friends/coworkers.

I did explain to him how I felt and he was very understanding, and I'm glad this happened because I do see a turning point where he is maturing and we can come to healthy conversations about our issues. He said from now on he would try to be more upfront and I will continue to try to also be understanding of his feelings as well. This may not seem like a big deal, but it makes me happy for the future.

TL;DR; Fiancé apologized and we communicated about how we feel.

(I also wanted to add a big thank you to everyone who posted. I read everyone's comments and and I appreciate the time taken with the thoughtful responses.)

( I wanted to add to those saying not to get married that I do understand the concern and I appreciate it, however we have always planned to have a long engagment. No wedding is being planned nor will be for a while, we are still growing up together. I really thought this post would only get a couple of comments but I am taking in what everyone is saying and will use it so we can communicate more effectively. Again, thank you everyone!)