In the end of last year Microsoft and its Live team faced a big issue of automatic vanishing of emails from several users Hotmail accounts (more than about 17K users.) And there was posting about such issues over and over last week on Windows Live Solution center but now they came up with solution. Hotmail team found the cause of the issue which led to the temporary lost of the mail box of the Hotmail account users. As per Windows Live they restored the account of impacted users of that concerned issue on Jan 2nd evening.
Still the Windows Live Team is investigating the issue, its root cause and making it sure that such kind of inconvenience not to happen again. It was to much embarrassing and shocking for the users but now all is well and team is recovering everything which was lost.
Source: Inside Windows Live