My good friend has invited everyone except me to his baby shower. How do I respond?

I’ve known Jordan since year 9 at school and we used to be in a lot of the same classes together and ended up hanging out in the same friendship group.
We also just so happened to land at the same university later on and we’d regularly meet up there and go out for Wetherspoons breakfast and so forth. While there, he met his girlfriend and they’ve been together now for about seven years.
I haven’t seen as much or spoken to him as much recently because they’ve been living and working up in Derby, while I’m still down in Bedfordshire.
Last time I saw him was Christmas Eve at a pub meet-up with our other friends. He told me then that his girlfriend was pregnant and that it was due in May and of course I was delighted.
Anyway, I’ve messaged him twice since then asking to meet and have a proper catch-up before the baby comes, but he’s ignored me both times.
The other day, I was speaking to one of our mutual friends who casually asked me if I was going to Jordan’s baby shower in a few weeks’ time. I said I didn’t even know one had been arranged, and he then told me that Jordan had made a group chat about it and everyone else in our friendship group was invited and he even told people in there not to tell me. He assumed he was just joking until I confirmed that I really didn’t know. Being the decent guy that he is, this friend has told me he now won’t go because of how I’ve been treated.
As it happens, I’m already doing something on that day so couldn’t have gone anyway, and I realise that baby showers are more of a girly thing, but the principle that he’s invited our whole group of male friends except me and made a point of specifically excluding me, I just find really hurtful. How do you think I should respond to this, because I don’t want to just shove it under the carpet and pretend it hasn’t happened? Should I message him, or his girlfriend (who I’ve always been on friendly terms with) or try something else? And what do I say?