Importing and exporting are never the correct way to transfer Outlook Data.
Hard to tell what you've lost.
Hopefully, all you've lost is the connection between the Outlook Address
Book and your current Contacts Folder. Just reset it. I'll assume you know
how already. You did not post your Outlook version.
For some versions, you only need to enable your Contacts Folder as an email
address book and make sure you add it here:
Tools > E-mail accounts > View or change existing directories or address
books > Outlook Address Book > Change.