Thunderbird->Mozilla lost mail

[frablac1]

After using Thunderbird .3 for a while, I wanted to try the built-in Mozilla mail manager. I first downloaded/ installed the 1.5 Mozilla upgrade, and set up my user mail account in it. Surprise! When I opened Mozilla mail, all my mail had disappeared. As I had neglected to retain mail copies in my Comcast mail account, I have lost stuff I really need.
Mozilla's mail client import tool offered imports from OE, Eudora etc, but not Thunderbird.
Next I looked for all *.slt files. The only one I found was for the account I had opened in Mozilla.
I guess I could buy an unerase utilty and look for my missing Thunderbird *.slt file, but I thought I'd ask first.