I'd contact Audible CS about your login credentials. The only way you're going to be able to play the files with their DRM intact is to have your device activated as a registered device.
When you say you "deactivated" your account do you mean you just canceled a membership (like gold or platinum where you get credits) or do you mean you literally contacted them and asked to have your account deleted? If the latter I don't know that anything can be done.
"The test of any good fiction is that you should care something for the characters; the good to succeed, the bad to fail. The trouble with most fiction is that you want them all to land in hell together, as quickly as possible."
— Mark Twain