Mel, your adsense code will be in one of two places. (1) google.com/adsense (2) Your cached blog pages (if they exist).

I would try 1 first, since unless you are able to login to the adsense dashboard, you are not going to make it very far with being an adsense publisher.

I believe they have a password reset/reminder routine or you can use their help section to retrieve your account details.

True, without your Adsense account it's pretty much useless to keep promoting Adsense.

I have my Adsense account setup to allow access from 3 seperate emails, better safe than sorry.