I know in some cases it can take some time for the ban to update on the website. If you don't see it right away, it may just take a bit for it to appear.
It sounds like someone other than yourself may have accessed the account while you weren't using it. I'd recommend getting in touch with the EA Help team when you've got a chance so they can take a look.
For more information on how to set up a case with them check out the EA Help website.