We had something similar happen. My husband had some financial issues before we were married. During our first year or two of marriage, we took care of everything. We've been married almost 10 years now, and 1-2 years ago, I received a call about a debt he had. They had all the right information too--social security #, prior addresses, etc. What they couldn't tell me is the origin, and why I had never heard from them before when obviously they knew how to find us, why I don't have something in writing, and why they didn't show up on his credit report. They just had a dollar amount and said he owed them money. I asked the man about the statute of limitations and he said there was no time frame on a debt. It was the strangest thing as we bought a house, various other things, his credit score was fine, and there was nothing negative any more on his report.
This company called us a couple times and then sent me a bill that just said he owed this money. The bill even said that they would take necessary steps to collect the money. I never received anything in writing as to details of the money owed as I demanded. I told them they needed to prove to us that he owed the money. Since I never heard from this place before, I wanted my husband's signatures showing he borrowed this money. Since they never provided that, I never did anything, and never heard from them again.
This is what I learned: a debt is still a debt, no matter how long...the creditor just can't get help from the courts to collect on it after the statute of limitations. There are companies out there that buy these old loans for pennies, and they try to collect on them. My guess is that when the bank took a loss on your home, they may have sold that loan to one of these companies for very little money, and that company is trying to collect.
I hope this helps a little. I'd ask someone you trust to verify what you've heard, and then you can decide what you should do.