At first, Kamala feared the Saroo was dead. However, after she found out about Guddu's death, she began to believe that Saroo was alive and lost.
When Guddu took Saroo on the train where he worked, Saroo couldn't have known that his brother would die during the trip. Guddu never came back for him because he couldn't; ultimately, Saroo was considered abandoned and was adopted by a couple in Australia.
Kamala, Saroo's birth mother, said that she started to fear the worst after the boys were missing for a few weeks. After a month, a policeman came to Kamala's house and showed her a picture of Guddu dead on the side of the train tracks. He'd been in an accident on the train where he worked. When Kamala saw the picture, she realized that Guddu was dead but that there was a chance Saroo was alive.
Kamala later tells Saroo that she didn't mourn him like she did Guddu because she believed he was alive. The family used all their extra money to try to find Saroo; they couldn't even make missing child posts, though, because they didn't have any pictures of him. She prayed for him, looked for guidance, and stayed in the same neighborhood in case Saroo came home.