You may be able to get a correction, but it is likely that it will involve dealing with your former boss. Even if you go straight to the journal that published the paper, they will need the current authors to agree to any correction. Yes, you should have been an author, but you should have responded to the PI when he/she tried to contact you. The PI probably could not include you as an author if he/she could not get in touch with you, as you would need to state that you agree with the contents, sign licensing forms, etc. If you cannot or do not want to be involved in any way with your former PI, there is no way to co-author papers with that person.