I'm having trouble with the Larceny quest, when i first played the quest i was able to give the final item (wont state what it is just for spoiler reasons) to Vex for the quest, but now it seems the quest ends when i first retrieve the item and it is no longer a quest item. I read that this is the norm now due to an update, just wondering, did Beth do this purposely so we could keep or sell the item, or is a bug? I would have liked to see it sitting on my desk in the Cistern...

I play on Xbox by the way and cannot use command codes to bypass my way around this..

Well, the larceny items are sold to Delvin, so there's your most likely problem.
Vex handles the Stones of Barnziah.

One you can't give Vex any Larceny items
Two you can't give the last item to Devlin either its a bug it hasn't been fixed

Delvin i mean >_<

Vex seems like a guys name to me so i keep getting his name wrong xD

If the item you mean comes in a pair then you can't sell it to Delvin. Put it in your house or sell it to one of the merchants around Skyrim.

this
you can only sell one to Delvin. You can sell the other one or keep it or whatever

You can't sell either to him. It's bugged.

Okay, yeah. Then it's what they said, it's a bug. It's happened to me. He won't buy either one.
The good news is though, if your speech is high enough you can get more for it than what Delvin would have given you.