Welp. Could be that they patched it. And it just occurred to me that it's possible that the character inspecting Alexandar needs decent Wits to pass.
EDIT: Actually, that's not it. I just reloaded a save and did it with 10 Wits.
But the dialog option specifically says "you take the gem from him". If this option shows up and does nothing then it's a bug. If it doesn't show up in the first place, then it's still possible that there's more to this.
Last edited by Try2Handing; 19/12/17 10:46 AM.