Not a big deal, or flat-out rude?

So last night my husband went to a party at a community house that we used to live in. The host of this party is a friend of my hubby's, but he doesn't know me too well. That being said, my husband was invited to this party and I was not!!
I assumed it was common courtesy to invite  both the husband and wife when there were lots of people involved. If it were a guy's night out or a small get-together or whatever, that totally makes sense, he's gotta have his free time, after all. But I was a little hurt when I heard after it was over that this was a large party and my husband went despite me not being invited. I told him I was so disappointed, and he said I was overreacting because the host shouldn't have to invite me if he doesn't know me!!
Am I totally overreacting, or do I have a right to be upset?