Hepzibah showed Riddle the locket and Hufflepuff's cup while he was working at Borgin and Burkes, and he stole both from her, ...

It was later purchased by Hepzibah Smith, along with Hufflepuff’s cup. Voldemort stole the locket and cup from Hepzibah Smith and used a Muggle vagrant's murder to create the Horcrux.