Have I broken a law here, and what are my options?

Someone owed me a lot of money, and paid me with a check from their home loan. I deposited it in the bank on Friday, and the bank put a hold on those funds until Tuesday.
On Tuesday, I went to the bank and had a cashiers check made, using the money I had just deposited. The bank manager and the teller both came to the window, and told me the check I deposited on Friday was now okay to use. I took the cashiers check to another bank, and paid off my house.
On Wednesday, the bank notified me that the first check I had deposited had bounced, and due to the cashiers check, my account was now overdrawn tens of thousands of dollars. The bank took all my savings to partially cover the overage, and I now have no access to money. On the other hand, I have inadvertently gotten an unsecured loan for tens of thousands of dollars they have no way to collect.
While we straighten this mess out, I am asking:
What if I walk away? Have I committed a crime like Bank Fraud since this was caused by the banks mistakingly approving drawing on funds they said were okay to use?