Sudden disappearance of emails

I logged into Outlook this morning to find that all of my business emails up until the 16th July 2013 had disappeared. I regularly log into my account although use the mail app on my macbook to read them predominantly. I migrated from Hotmail about six months ago. The Microsoft chat man took me through all the usual recovery actions but to no avail. I am incredibly annoyed that all my emailing over the past couple of years which is vital to my business has apparently gone. Is there a  way of checking what might have happened?