This is why you should always ask questions and never stop asking.
If you aren't happy with the treatment you're receiving, you have a legal right to request all of your medical records (though they will try the "We lost them" ploy) and if need be ask for a second opinion.
Please ensure you have a family member or an advocate, who can and will ask all those awkward questions you can't or are too ill to ask, before and after a procedure is carried out, and always have someone to support and be with you.
This really in more than a Tragic Mistake and no apology is every good enough!!