Missing Body Content of Inbox & Sent Box Emails

Messages I had saved in my inbox and sent box between April 20th to June 1st 2009 are no longer available. While I can open past emails, the "body of content" is empty, and the recipient has changed to undisclosed? What's going on here? Is this an error with Yahoo, or did someone compromise my email service?

Also, i filled out a Yahoo ticket? Do they archive my emails?