I went over to the New tab because I missed some things from Latest apparently, and I had an unlisted thread appear in the list. The forum it happened on is a private one, but the Discourse staff have an account there. Link to unlisted thread that showed up in New.
I can’t. I’m not sure how unlisted topics work, but did you set it as unlisted before it was posted (not sure if people with appropriate permissions can do that)? Or did you set it to unlisted after it was initially posted public? If that doesn’t get it to show up in New, maybe the key thing is locking it before unlisting it? Maybe the thread mentioned in OP showing up in New was just a fluke?
yes that makes the difference, we don’t send a “live update” to all clients telling them a topic became unlisted and must be removed from all “new/latest” lists, we should do that.
I will leave this under bug but it is very subtle.