Perhaps it was not odd that he picked it up. I remember that one of the Bloodguard picked up one of the Ramen's garroting cords and snapped it, as if to say, "see how useless weapons are?" So perhaps Korik thought he would crush the stone in his mighty Haruchai grasp or something. But when he picked it up and started gushing to all the other Bloodguard about how awesome it was, shouldn't someone have snapped his neck or something?
On top of that, Korik and two other Bloodguard intended to deliver the stone to Revelstone, but they sent other Bloodguard ahead of them to Revelstone. Why not all go together? Was he already Corrupted at that point?
Going along these trains of thought, it makes me think about the Haruchai mental communication. If Korik was Corrupted upon contact with the Illearth Stone, perhaps he became viral and could infect the other Bloodgurad through telepathy. Perhaps that is why no one broke his neck. Perhaps Korik's trio had planned to go fight Foul from the beginning.
And furthermore, they got PUNK'd by that Raver. Kinslaughterer had already accomplished his mission of genocide. I believe that he dropped the Stone on purpose to Corrupt the Bloodguard. I think the Corruption of the Bloodguard was part of Foul's plan all along.