Harrington became separated from her friends after she left the concert arena Oct. 17 and was denied re-entry. She told them she would find a way home.
Investigators want to hear from anyone who might have loaned a cell phone to a woman fitting Harrington's description, police said.
Harrington was wearing a distinctive necklace made of large crystal chain links, police said.
Metallica is offering $50,000 for information in the search for Harrington. Jefferson Area Crime Stoppers is offering $100,000.