With the new steal system, when you steal from an enemy, if the stealing is successful you'll get the item in that enemy's inventory.
A common method of setting enemies up in WC3 maps is placing them on an inaccessible place, then move them to their area when they become relevant. This inaccessible place in chapter 6 is the parapet at the northwest corner of the temple.
For some reason, Jurxy drops the Amulet of Great Magic, which is supposed to be stealable from him, when the map initialises.
So it can't be stolen from him, but using Vacuum when standing near that parapet can pull it down.