[djeikyb]

Facebook could have stored your email address as part of your friend's account, eg "an email address this person is friendly with". Your account, posts and friends and all, are gone, but you leave traces of yourself with your friends. These traces could be reconstructed.

[CGamesPlay]

Without knowing the exact details of your case, this sounds like the correct explanation. The friends you saw were probably ones who have used Facebook's contact importer, and so their accounts had a record that your email address was a known contact. All of your wall posts, photos, friend lists, and other activity were actually dropped from Facebook's databases.