Rosa Quituisaca said she got a call last year from a friend warning that the two of them might have made a mistake buying homes from the same Hamptons property investor. The friend said the investor was asking for more money than he had initially agreed to pay. Quituisaca soon found problems of her own. She discovered that the deed for her $475,000 East Hampton home had never been filed, leaving Suffolk County without any record of her ownership. When the deed was later recorded, the purchase...