From my understanding, admins can "remove" communities, and mods can "delete" them. The effect is similar for users in both cases, and the difference is in who can restore the community.
This case looks like some kind of federation issue with LW. Maybe that community was briefly deleted/removed as a test, but the undo action didn't federate over to us? The only record I can find about this community is the restore action from 2 days ago