Borderlands 1: Where is the Eridian item I just picked up?

I just defeated the Rakkinishu during one of the Hidden Journal quests. Among the Cracked Sash and the other standard loot, it also dropped some Eridian item (I didn't fully read its name). But now I can't find it in the inventory. It's neither in the weapon/item list nor in the artifact list. It's not on the ground either; I definitely picked it up. What's going on here?