We had a moderator accidentally delete a user who posted a topic instead of the one who posted spam at the end of it… aside from the badness of not being able to undo deleting the user this caused the first post of the topic (i.e the topic itself) to end up in a deleted state. assigning the topic to a new user left the first post in the topic in the deleted state with no way to recover.
the lil trash can icon under the post would let me delete the entire thread and then the undelete icon would come up and let me undelete the whole thread. after doing that the first post was still stuck in the deleted state.
I ended up undeleting the first post manually via the api which fixed the problem.
however it would be nice if it was possible to fix this via the UI. i.e the undelete button should probably have been available on the first post when the thread was not deleted but the first post was. if that isn’t reasonable perhaps undeleting a thread should also undelete the first post in the thread if it is in a deleted state.