Its an interesting question, but I would encourage you to hire an attorney to go any further. I'm just guessing here, but I think you will find that the bank still has the write to collect their asset. My understanding is that the lien provides them rights in the order of default and creates a claim against the property should you fail to pay. In the end it establishes the order of payment of any proceeds. I'm also pretty certain that you signed a mortgage that contained a "due on sale" clause that gives them the right to foreclose the property - even without a lien. Teh major question would be how do those two facts interface with MN statute and case law.
An attorney is definitely the way to go. You will likely be able to get your questions answered in a quick phone consultation.
THIS IS NOT LEGAL ADVICE BECAUSE I AM NOT AN ATTORNEY.
Coldwell Banker Burnet
licensed MN Real Estate Broker