I had accidentally done this as well. I meant to dismantle another legendary in order to obtain some ascendant shards. So I wound up dismantling both, and then I received no glimmer or materials for either legendary that was dismantled. Now I'm out my legendary scout and pistol and still don't have enough ascendant shards to level up any of the equipment I already have maxed as far as XP is concerned. Ascendant shards are so ridiculously rare, and the equipment requires so much that I am at a point where I need roughly 36 of them to actually acquire bonuses/light on armor I have long since unlocked all bonuses for purchase. At the rate this is currently going, along with my being denied my materials bonuses, I don't see how I'm going to level up any further.