old Outlook account & contacts

Hello, I recently deleted a very old account in my co-worker's Outlook. There were no emails in the folder, and I thought it was safe to delete because it hasnt' been used in years. However, it seems that when I deleted this account it also deleted all her contacts! I would like to first know how to fix it (I left the old .pst file on her desktop, so perhaps it's as simple as putting it back in the Outlook folder), and second I'd like to know how/why the contacts were saving to an account that wasn't being used.

The answer is here: Import email, contacts, and calendar from an Outlook .pst file - Office Support