I wouldn't worry about future employment. EEOC regs allow people to ask if you worked there, when, and would they re-hire you. They of course will say they won't re-hire you but the potential employer cannot ask why. If they do ask why and that question is answered, you may feel free to hire any contingency attorney and sue them into next week. My suggestion, as VP of sales and an interviewer of sales folks, is to do the following:
1) Update your resume as normal
2) When asked why you were at your last position for such a short period, answer honestly that you believed you were dealing with a concerned mother...any reasonable person would want to help a concerned mother....the reasonable man test is passed. DO NOT LIE about it.
They will KNOW that you understand the confidentiality issues at this point...you got fired for it so that isn't going to be an issue in the future.
This probably worries them from a identity theft perspective as well...the daughter is an idiot for having her bank account closed for overdraft excesses....if she is that broke, she will sue the bank anyway. That is a crappy lawyer's nirvana...taking that position, you may want to tell your boss that..."we are probably going to be sued anyway...why not put me through additional training, work up an new confidentiality agreement to sign and that will be the actions that the judge sees that you have taken". It probably won't work but its infinitely less expensive than interviewing, hiring, and training a new employee.
You will be fine sir....it might not hurt to resign either...do it now and write a resignation letter that you can show to your next employer. That way you were NOT fired. If they ask why you resigned, be honest...you were manipulated by a customer with malicious intent and didn't want to be a casualty of the bank's lack of understanding the situation.
In truth, you didn't actually violate your contract if I am reading this correctly. Technically, the daughter was not a customer of the bank...the bank closed her account. What is the definition of a "customer"...does your contract say "past and current customer's" or just customer. Perhaps that technicality will allow your supervisor to take PAUSE before letting you go...after all, depending upon the language in the contract, the bank might be getting sued by the daughter AND by you for an unjustified release. Now, if you live in a right-to-work state like Texas, employers can fire you at will, and without reason.
Good luck to you,
Changeup