the locket story is introduced in the goal line below. It ended in limbo until we started getting Monster Hunts. Once traded for in the Trade Wagon, the storyline again just ends. There are no other goals triggered by this storyline.
Extract taken from the Story Outline guide (link below)
32. Poof and Gone
The Locket is still missing at time of writing this guide.... the story just stopped here and hasn't been picked up again. SW April 2015
Update: April 2016. The locket has been found and is available for 5 gold tokens in the trade wagon.