Work Xmas party dilemma

Morrissey
Not sure if I'm overreacting but I'm a bit cranky, I found out my work Christmas party is tonight as people are posting photos on Facebook and I wasn't invited! I'm currently on parental leave (I'm in Australia so 7 months into my 12 months off) none of the other women on parental leave were invited either.
Am I being silly by being annoyed? I'm still an employee of the company and just think it's a bit rude to not get invited.