No need to be upset, but it's fair enough to point out that no one comes back to work as if they haven't left after a year off - doesn't matter if it's a woman on maternity leave or a man who took a sabbatical. It takes some time to catch up. No need to take everything personally.
I came back from mat leave to the promotion I won when 8 months pregnant. No issues. Probably easier than going back to my existing post in terms of ‘catching up’.
If you were in the market for promotion you should have kept your eye on it then.
I’m not sure it meets the bar of reasonableness to expect someone to check their work emails on a very regular basis while on maternity leave on the offchance an appropriate job might be advertised. The burden on the manager to do this is much lower (curtainsy is eligible for that, I’ll forward it to her) than on the person on mat leave (log on once a week, trawl through emails on the offchance there’s been an appropriate job opening in the team, even assuming you still have access to work systems while on mat leave, even if they have remote access usually.
Many organisations will suspect IT accounts, mailboxes etc if people are on leave for more than a stated period, eg 3 months in several places I’ve worked. This saves money. Some people don’t have remote access at all - should they drop by work once a week to check for jobs?
It’s the responsibility of the organisation to ensure those on mat leave aren’t treated unfavourably compared to colleagues. Not being informed in a reasonable way about a promotion for which she was eligible is unfavourable treatment.
I really hope none of the ‘you should have kept an eye on your emails’ posters are managers. Managers still have responsibilities to their staff on parental leave.