Ctrl+K is the keystroke for address resolution, not searching.

The process of adding another user's Contacts folder to your own address
book display is somewhat involved:

1. Start with a profile that logs directly onto the other user's mailbox,
not your own.

2. On the Properties dialog for the other user's Contacts folder, make sure
that it's set to display in the Outlook Address Book and give it a display
name other than contacts, such as Joe's Contacts.

3. Close Outlook.

4. In Control Panel | Mail, edit the *same profile* to change the mailbox
from the other user's to your own. On the Advanced tab of the Exchange
Server service, add the other user's mailbox as a secondary mailbox.

5. Restart Outlook, and you should see the Joe's Contacts in your Outlook
Address Book as well as your own Contacts folder.