That’s right BobTI. The contact conversation does go missing from the list. I guess the idea of pinning the contact made it easy to start the next message again rather than having to go back to the main contacts app on the phone.
One idea is that you can enter the contact name and their phone number into the Notes app. That way you can easily create a list of regular contacts you stay in touch with and you can press/hold their phone number in order to send a message via the Notes app. This means you can delete them off of the messages app and easily send a message to them through the Notes app. And avoid having a bunch of contacts pinned to the top of the messages app. which is possibly not a good thing for you.
With my work, I do a daily list of clients up that have to be messaged, on my desktop PC, in the notes section of iCloud which then shows up on my phone and I do the initial messaging from my phone in the Notes app. I Manage the replies and any ongoing message conversation through the messages app.
So, I’m saying that it’s really easy to make a good phone list in the Notes app. and use that as your contacts list. Then, it doesn’t matter if you delete them off of the messages app. list.
ideally, it’d be great if Apple would just put things back the way that they were but somehow I don’t think that’s going to happen.
I hope this helps you out. Cheers. Andrew.