That's good news for you! If the lender "lost" your original note, then they have great hurdles to go over to prove that they have the right to enforce the note, mortgage debt, and foreclose. It sounds like you are amidst a foreclosure fraud case, one of many that are taking place nowadays.
My suggestion: check all of your documents and look for fraud... were there any missing official assignments that were never put on record? Are there "robo-signers" on your documents?
Check your state and local foreclosure laws and make sure that the foreclosure process is being followed to a T. Many times it is not, and you can challenge them on several accounts.
I personally know several people who have challenged banks and lenders about their mortgage and won because the Banks and Lenders couldn't prove they actually held the mortgage note and could foreclose - or how they got the note through a complete chain of unbroken endorsements.
Best of luck and I hope that helps!