Question about Outlook Express

I converted from hotmail to outlook approx. 150 days ago.  The conversion information indicated no emails/folders would be lost through the change.   An estate litigation has heated up again, and yesterday I learned that a significant number of emails, saved and meticulously compiled between 2009-2011, are now gone.  Microsoft support says they have a dedicated team to assist, but can't get through to an agent at 1-800-386-5550.  I am a paid subscriber.