Is there any way that these messages could have expired and been rendered inaccessible overnight? I hope they aren't deleted. Did you try searching the drive(s) for the PST with admin rights?
MS isn't super-helpful here, but the following may give you some hints. One item doesn't sound too good, so best of luck to you.
http://support.microsoft.com/kb/830119/
"Your existing folder structure is maintained in your new archive file. If there is a parent folder above the folder that you archived, the parent folder is created in the archive file, but the items that are in the parent folder are not archived. In this way, the same folder structure exists between the archive file and your mailbox. Folders are left in place after being archived, even if they are empty. You can only archive one file type, a .pst file."
http://support.microsoft.com/kb/813605
Archived file data is lost if you use Windows Explorer to open an archive file from Outlook 2003
http://support.microsoft.com/kb/297019/
Personal folder files are unsupported over a LAN or over a WAN link
edit: This was just archiving, right? The words "transfer" and "move" have me wondering if this didn't occur between 2 different machines.