Hepzibah showed Riddle the locket and Hufflepuff's cup while he was working at Borgin and Burkes, and he stole both from her, using the murder of a Muggle vagrant to create the locket Horcrux.

After Ron's suggestion that they could use basilisk fangs in the Chamber of Secrets to destroy Hufflepuff's cup, she finally ...

Harry and Dumbledore study Voldemort's past to find his Horcruxes in Harry Potter ... a descendant of Helga Hufflepuff, who had Hufflepuff's cup and Slytherin's locket. Voldemort killed Hepzibah ...

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.