Everything is going great, you are in work on the weekend (ok, maybe not), and then poof! Your colleague looks at you and says that his inbox is gone. He can access it from his iPhone, but that is it. A quick google search brings us to the article below. Somehow his Inbox had the hidden property set which prevented it from being shown in Outlook 2007.
http://ozgrant.com/2007/07/24/fix-outlook-inbox-missing-disappeared/
Hope this helps someone else to resolve this issue.