There are some items that aren't obtainable at all.
CipSoft has done this in the past and does it to this day.
This is done as an incentive for people to search for the item, same thing happens to quests, some quests are not finished on purpose.
Either way, there are items that are no longer obtainable at all.
The only way that happened back then was a GameMaster would create the item and hand out to winners of contests, there are no more GameMasters today specifically to avoid exploiting this. (There are cases where a GameMaster has benefited a friend with items). Rarely, Community Managers log in and they too can create items, but they're under heavy surveilance nowadays, it's unlikely that he'd spawn a known 'very very rare item' without being pubically announced.