I was at Pit of Saron where at final boss I rolled for Nevermelting Ice Crystal and I won it. But received nothing, I tried to loot the boss, nothing happened, then I tried to relog which let to an exception and the game crashed. I already own this trinket and have it equiped but I wanted to use it for my other slot as well, maybe this has something to do ? Still even so, I should have at least get the thing in my inventory.
It's unique, not unique equipped. Meaning you can only have one of those.
Unique-equipped means you can have only one equipped, but there's no limit to how many you can have in inventory/bank.