I'm playing a fully updated Skyrim for the Xbox and am sitting on 22 stones of Barenziah. I've hit all 24 locations, and gone over them all again with a fine-toothed comb. I got every one of them, but I only have 22 in my inventory. I do seem to remember having four or so before showing them to Vex - remember that at this point they would have stacked. Now there are only two in a stack, and the other 20 are listed as unique. Is it possible for the game to have deleted two of them? Also, that appraisal conversation with Vex is repeatable (I have no idea if that's pertinent or not, but there you go). Is there a workaround here?