[Dovecot] help with deleted segment of email when connecting Outlook?

This group was so helpful last time I am hoping someone can HELP! We have qmail / dovecot running IMAP and a user who had all their email in their non-Outlook client (Thunderbird?). We installed Outlook 2003 and configured it with IMAP and all their email EXCEPT a three week block showed up. The three week block of email is not on their desktop and even worse, isn't on the server / in qmail - its totally gone.

Does anyone have any idea of why or how this would have occured? And even better - is there any hope we could ever find this email (its not on a backup)? Hopefully,

Lisa