Once you get back into the machine, you'll retain all of the memory links. So go ahead and interact with the soccer ball memento.
After the cutscene interact with the soccer ball that's in the white space and you'll get sent over to an earlier memory of Johnny.
Within the memory, leave the backyard and head south of the street. You'll find Johnny playing with his soccer ball on the left sidewalk. Interact with him.
Now keep going to the right until a cutscene play. When it does, head back out the street and to the car parked near the backyard entrance. Prepare for the long cutscene. Interact with the event Johnny after the cutscene to move onto the next memory.