Product: Checking or savings account

My wife and I got divorced on XX/XX/XXXX. After the divorce, some newly discovered funds came through in the form of an escrow refund check from US Bank Mortgage. Per our decree, newly discovered funds are to be split XX/XX/XXXX. 
We have had money escrowed for the last 6 months to a year included with our mortgage payments from XX/XX/XXXX and prior. These funds were escrowed to eventually pay our XXXX XX/XX/XXXX property taxes and annual homeowner 's insurance policy. Since we got divorced on XX/XX/XXXX, we did not need to pay this bill and the money was refunded to both of us in the amount of {$4100.00}. The refund check went to my ex-wife 's address only, had my name listed first, then my ex-wife 's name was listed second. There was no " or '' or comma in between our names, and she cashed it by only endorsing her name. I have been informed that this should have been rejected since both of our names are on the check. The US Bank teller failed in this instance by cashing it, and my ex-wife committed fraud in cashing it. She will not return the funds and I have asked several times. 
I have a copy of the check, the account number of the check, the mortgage account number, and the statement that was mailed to me to which was the only way I would have discovered that this fraudulent activity took place. 
I have been researching and talking to the US Bank Fraud Liaison Department which handles their banking fraud, and the US Bank Mortgage division who handles mortgage fraud. Everyone has agreed this is 100 % fraud. 
After getting transferred back and forth between the banking Fraud Liaison Department and the US Bank Mortgage division for the last 2 months, being told a fraud case had been opened on the banking side to later find out it was cancelled since it needs to go to mortgage, I finally got to someone high enough and with the wherewithal to handle this. My most current contact is on the mortgage side and his name is XXXX XXXX who reports directly to the USBank Mortgage president. They have said for over a week that an affidavit is being mailed to me to which I must promptly return for them to start the investigation. This is the 3rd time since XXXX where I have been told an affidavit is coming. This time, I have been assured it truly is coming. They say they always start from the beginning, and they will start the investigation on the Mortgage side which is their policy, and then take it to where it needs to go from there. 
As I mentioned, for a while, I was getting the runaround with all contacts at USBank. Most likely this is because my ex-wife is an employee there, and she had to take this check to a teller she knows within her branch to get this fraudulently cashed. Being a nearly XXXX employee, she knows banking practices and the law, and she knows this was fraudulent which was the only way this would have gotten through. I have verified this as the case per the contacts I have spoken with at USBank fraud, USBank Mortgage, and others. 
I have setup a case with the XXXX, IA police department as well. It is case # XXXX. The police chief is XXXX XXXX and his email address is XXXX and their phone number is XXXX. He has emailed me a few times stating he believes this is more of a civil matter, but he will help me any way he can. He has contacted the XXXX XXXX Iowa attorney. 
I contacted the Iowa XXXX XXXX over the weekend, and they referred me to you, the XXXX, and they mentioned I may want to get in touch with the Iowa XXXX XXXX XXXX  at the state level. They thought I may want to get in touch with the FDIC at the national level, but your rep, XXXX XXXX XXXX XXXX ), said you will handle contacting the FDIC if necessary. 
I have been taking notes of nearly every conversation with every person to which I have conversed since XXXX. I can provide any supporting documentation to which you may need including the endorsed check, the mortgage statement showing the refund, and all conversations. 
The US Bank Mortgage department only gives me their customer service number which is : XXXX and I have to get transferred several times until they get me to XXXX XXXX who reports to the US Bank Mortgage XXXX. 
The US Bank Fraud Liaison department can be contacted at : XXXX. XXXX has been my main contact there and her employee ID is XXXX. The auditors are XXXX and XXXX. That's the best information she could give me on them. 
Thank you for your assistance.