The answer to this question can be found in the closing paragraphs of chapter 7 and the beginning paragraphs of chapter 8. Chapter 7 sees John and Lorraine at Mr. Pignati's house in the evening, and Mr. Pignati is quite happy to see the two teenagers. He tells John and Lorraine to make themselves at home, and he lets the two kids explore his house. Lorraine finds a picture of Mr. Pignati's wife as a young girl in a confirmation dress. John continues snooping around the house, and he probably oversteps his bounds by going through drawers. In one drawer he finds a pamphlet from a funeral home. Next, he finds a bill from the funeral home and Conchetta's social security card. This confirms to John that Mrs. Pignati is not in California. She is dead, and chapter 8 begins with John telling Lorraine.
"His wife’s dead!” John whispered.
“I just found her funeral bill.”