It isnt always true that you cant recover the mail..
There is a very slim possibility.. But its still a possibility..
That if you hurry and contact windows live support.. you can get them to save the mail.
Just because it gets deleted of your inbox, and account
Does not mean its deleted of their server..
Immediately.. go to the link below.
click ask a question.. Tell them you are missing very important mail you didnt delete.. And you want to know if they can save it off their server before its permanently deleted..
If your very lucky, one of the support techs will see it and help you before its too late.
Now.. lets cover a reason this could have happened.
Your account could have been hacked..
Someone could be accessing your account and deleting the mails..
to make sure that is not happening.. Please immediately change your password, secret questions and answers, and also your backup email..
Do this now as well, As dissapearing email is suspicious account activity and often the first sign you have been compromised..