Mail Rebuild=Missing Messages

Yes I know, outdated tech. But I use a Powermac G4 for my email. I am running OS X 10.3.9.

Recently, all my emails in one box, that had 6000 emails in it approximately, were showing, can not display, must connect to server to read errors, and wouldn't let me transfer them to other mailboxes. However, I have my email set to pull down all the email off the server when it retrieves it so I know that it's on the computer, and no longer on my server (TWC, they don't allow much space). SO the error was incorrect, it just wasn't showing them for some reason.

SO I did a rebuild. As soon as I did it all my emails dissappeared. Not a sigle one was left- in that mailbox folder. Every other one was ok.

Upon some internet advice I went, found the mailbox and inspected it to see it's size. It's 1.7 gigs, so I am assuming that all the data is still there.

The question is, how do I get hte messages to show up again in Mail? This has been crazy frustrating and nothing I seem to do works. Including moving the Mail folder out of the licrary and those sorts of things. I haven't moved any plist stuff yet as that seemed chancy.

Help!