It was your responsibility to report the loss of your card.. However, you may still be entitled to relief. Go speak in person with a consumer debt attorney or a lawyer with experience handling identity theft. There is little we can do here to help you as this is a simple online Q&A forum and your problem is too complex for sufficient help here.
It sounds like you want to know if you are obligated to cover the wrongful charge from your savings. I agree that you need to talk to someone to get a more informed answer. Generally, though, you need to be a self-advocate. Write everything down, send it or email it to the bnk, and keep a copy. If your card was stolen (not lost) it is not too late to file a police report. Good luck!
Answering this question does not set up a attorney-client relationship between us. My comments do not constitute legal advice. If you would like to pursue representation, please contact me.