Please allow me to respond immediately after posting your opening statements of the alleged problem; you first said: "3 weeks ago when logged into my online banking site, within seconds my screen showed my account balance increased from $50 to $50,000, then back to $50." Right?
Response: Unless I suddenly lost my ability to read plain English, all you had in your account was $50 when this problem started; right? Then suddenly you had $50,050; right? And then a few seconds later your account balance went from $50,050 back down to $50; right? So then where is the beef? Why do you think you should get to keep the mysterious $50,000?
Here is your next statement: "I immediately logged out of the site and called my bank's fraud line to alert them that something had happened on my account. I was told by the bank that my account would immediately be frozen." Nothing to see here. When you reported this apparent money laundering scheme your bank did exactly what your bank should have done: Froze you account.
Finally, having operated the money desk at a large international bank in Miami and having investigated scores of similar stories of money laundering, check kiting and many other tricks people use to steal money I noticed a glaring "tell" a few statements later in your recitation of the facts: Here is the tell: "I had a joint checking account at this bank with my elderly father and his bank statement notes a "forced check pc transfer" for $50,000 debiting his account." I do not want to jump to any early conclusion here but this is the reason BOTH accounts have been frozen.
P.S. Removing your name from your father's account was not helpful; in fact it makes you loot even more guilty--in the bank's eyes.