Precious items are regular items that are found within the game and for which a player has registered to become autoloading. Items are often available to be made precious following a Kleiburn auction or holiday events where players may obtain more rare items.
If you lose a precious item, for whatever reason, you may always resummon it via the Special command.
Precious items, being temporary, have an expiration to them. You may, at any time, review the date at which such items will expire via the OOC command. Threshold has a daily routine to check at 6AM ET for those expirations and remove those expired objects from the game.
If one of those items is a container, you should probably have emptied it of its contents ahead of time. Who knows what may happen to treasure that was contained within at the time the expired object is removed?