Reset Last Mail Downloaded - POP not IMAP

Where is the information identifying the last mail downloaded stored?

During a mail check (POP not IMAP) for some reason Pandora shut down. When I restarted it messages that should have downloaded were missing. On the server they are shown as downloaded.

Is there some way to reset the indicator to what it was before the last download?

Thanks,
Les

Personality > Right-click/View Mail on Server

Right-click on message summary > Choose action that will be performed on next mail check: Leave, Fetch, Delete, Fetch then Delete

This won't solve my issue. The "lost" messages are not in the message summary.