Mozilla Mail- HELP!

[Mnemosyne]

Last night I used IE to view films at ifilm, works better than Mozilla. Anyway, this a.m. when I go to check mail, ALL of my saved emails, files and setup info is GONE!! I tried to compose and get setup account screen. The only thing there is my address book listings.
I had emails from Helen Thomas and John Conyers, personal emails, not newsletters. These were precious to me.
Can anyone tell me what may have happened? Can I retrieve my files? How?

My deepest gratitude to anyone that can help me.
I have an appt. in a short while and will login later.

Thank you!

Vicki