A locket is currently a useless item, and often considered as junk.
A locket is a jewelry item and has no use, being added purely for the purpose of clutter, creating more realism for the player when looting.
A locket can be found on corpses, in purses and in some stores.
From newitems.txt (Project Zomboid directory/media/scripts/)
Weight = 0.5,
Type = Normal,
DisplayName = Locket,
Icon = Locket,
MetalValue = 10,