the lost thing

When the boy first finds the strange looking thing, he says that the people around him didn't notice its existence because they were too busy with what they were doing. Also at the end of the story, the boy says that he could see less lost things than before but actually there were many lost things drawn around the boy. In this scene the boy has grown up and is wearing a suit, so probably he is a business man or something... therefore, i thought maybe "the lost thing" could be things we tend to forget in our busy daily life. Something we have in our childhood and lose as we grow up... I wonder what that could be!! perhaps it differs from person to person but imagination could be one thing.