Matt, by design, the first 400 recent messages will be displayed when you search in your Windows Live Hotmail account. This is why you can’t see your older messages from the search result. For example, you searched for the word “hotmail” in your e-mail account and you have 500 messages containing the word “hotmail,” the first 400 recent messages will be displayed.
As a workaround, you may access your account in an email client. For further instructions, visit this link:
http://windowslivehelp.com/solutions/settings/archive/2009/01/06/send-and-receive-windows-live-hotmail-emails-from-a-mail-client.aspx