The federal protection for tenants after foreclosure expired in 2015 and was not extended. But even that only gave 90 days before you could be evicted through the courts.
I don't see anything in MO landlord tenant laws that allows you to remain after foreclosure:
http://revisor.mo.gov/main/OneChapter.aspx?chapter=441
Now that the bank owns the property you WILL have to leave. Whether you leave as a result of written notice of termination or eviction through the courts, you WILL be leaving at some point and, trust me, you don't want a court eviction on your credit report.
Meantime, if you believe that your landlord breached his contract with you, you are welcome to sue him in small claims court for whatever dollars you think he owes you but you'll be doing it from somewhere else, not from where you are living now.
PS: You won't have to move "suddenly." If you haven't received termination notice from the bank, you still have time. Use it wisely, by finding another place to live as soon as you can. Don't wait until the last minute and then complain that you have to move "suddenly."