Employment Law Help

I work for a public sector organization in Ontario. I’m currently on maternity leave and the person they have filling in for me is getting a promotion to a step above my position but I wasn’t offered or even informed of this. I had to hear it from a third party and not my own boss. I’m not unionized but I am in an employee group. Is there anything I can do, or do I just swallow it and the embarrassment this is going to cause me when I go back.

Sorry I know this sounds kind of whinny but I’ve been working there for 6 years and have always been told I do my job well. Then I go on maternity leave and this person fills in for less than a year and gets the promotion I’ve been working for. Just seems so unfair.