Mateo?
Is this for becoming the member of the thief guild quest?
IIRC, I read something about those name mistakes.
Anyway, I belive you must use pickpocket on Sweenie (or something like that).
Look at the "x" under necklace theft on the screenshot:
You must pickpocket person that is standing there:
Btw, welcome on the forum. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />