Outlook 2013 Standard Edition - Contacts Auto-Complete Lost

I am using Outlook 2013 Standard Edition and it seemed that we had a Power-Cut yesterday evening. Now, whenever I try and write a new e-mail, all the autocomplete contacts (drop-down menu) are not there anymore and I have to type the full e-mail address.

Does anyone know a way on how to get them back? They must be stored on the computer somewhere. I'd appreciate any responses as this case is quite urgent.
 
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