“Upgrade” to outlook deleted all my emails?

I have been logging in via web client to make sure my hotmail wasn't flagged as inactive. I log on to find that I've been automatically "upgraded" to outlook and ALL my emails are gone. Over 10 years worth of email gone in an instant. And I have a pending court case with a receipt from that mailbox that I absolutely NEED! I have tried recovering deleted messages but I get this: (Sorry, we've tried our best, but unfortunately there are no mails to recover.)