Did you get your original Note back stamped canceled? If not, the bank is free to sell it forward to someone else which is exactly what they are doing (or putting that Note into another active Trust)
If your mortgage note was securitized into a mortgage-backed security and transferred (unlikely) to a Trust, then go to the SEC site and get the Prospectus for that Trust. One of the sections in the prospectus states that the “funds from the investors will be used to BUY the mortgage notes”. Therefore, the investors paid for the NOTES and none of the banks have skin in the game, so to speak. If you can’t find your Trust number, chances are the that Trust has been paid down and is no longer active.