Primary email account disappeared iPhone

Hello --
I set up my two email accounts shortly after buying my iPhone six days ago and theyve been working fine. Until this evening, when I discovered that my primary account simply vanished. Im quite certain I didnt go into Settings, then scroll down to Mail, then tap that account and hit the big red delete button.
Apologies for being snarky, but Ive spent an hour trying to get it back online again (to no avail), will now be without access to my email all day tomorrow and I really dont want this to happen again. Any ideas on how to ensure it doesnt get nuked in the future?
Many thanks,
Sean
Mac Pro 2.66 Mac OS X (10.4.6) PowerBook G4 667