A real estate closing is an anxiety-inducing time, even if it goes smoothly. Add something unexpected, and it will throw you for a loop. I was thrilled when the sellers accepted my offer on a tear-down lot in McLean, VA, the perfect place to build my own “Downton Abbey”–style manor. And the deal went forward without a hitch—that is, until closing day. Soon after I arrived at the title company's office on the big day, my real estate agent sheepishly handed me a set of 40-year-