There are other ways of earning slots (login rewards, token vendor, slot-related events).
The game doesn't do this, login reward slot drops are random based on slot rarity.
Not all vanities were meant to be limited quantity. Leaderboard vanities are limited quantity. Anything from the Platinum Store is limited in quantity (auras, vanities, and guaranteed badges). However, I think if you're acquired an event crate you should be able to get what was available at the time the event was run even if you opened it after the event concluded.
-ALS
Bookmarks