It’s actually possible to get up to 3 ascension items.
Basically, the star rating of the titan and your perfomrance score combine to give you your ‘loot tier’.
Each loot tier has a set of number of ‘chances’ for various categories such as food, iron, forge ingredients, summon tokens, gems, flasks and ascension materials.
You got Loot Tier XI here but I think anything from tier IX onwards gives you 3 separate rolls at getting ascension materials.
So, you could lose all 3 rolls and get no ascension materials, get 3 wooden swords or, in what I would image are spectacularly rare chances, pick up 3 lots of top level ascension materials