You have a very unique excuse for your ban but I don't think you being not the one who posted the plagiarized post/s can help you save your account. Sad to see your account go but you should have at least took the time to look the posts you have bought from your friend whether or not it is plagiarized. This does not absolve someone who in his account posted the plagiarized content. The way I see it is if they let them give you a chance a lot of people will see this as an opportunity that doing plagiarism in the forum is ok and they do have the chance to walk away freely.