If you have some website that you never have any traffic on, there would A: be no reason to hack it, and B: no one to know there's a website to be hacked. If you want to design a website that is totally unhackable, just design a website no one will ever get to... However, that kind of defeats the purpose of having a website in the first place.
Even though hackers look to attain certain information there is a publisher who did activate software to stop a potential hacker. However, there has been a huge level of incompliance concerning those involved. Several have involved themselves in the life of that publisher without approval and the legal officials that assisted in the production of the software are no longer living leaving that publisher as a stand still while justice prevails. That publisher did not ask for assistance where others have stepped in and the security was compromised multiple times due to the lapse in compliance. It is possible to keep a site free of hackers with full cooperation of international figures and safely precautions that need to be taken seriously.
I would look at it as though your information could be captured regardless of what site you are on. Go ahead and assume that someone or something is following your every move, because that is likely the case. We have governments spying on us, all of us. There is no way to ensure security under these governments and assuming it is there, is foolish.
No, there are not any true sites that do not have the possibility of being hacked, because everything is vulnerable to some kind of breach. A prisoner recently escaped from a high security prison in Michigan. If there is someone willing to breach security and help out, even the most security of websites can be hacked.
Any sites that are created and managed by humans have the possibility of being hacked by other humans. We are all prone to error and some one out there will be able to expose any small crack in the security and hack any given website on any given day. For every person that is gifted in website security management there is another person who is equally gifted in hacking.