Are you sure about that? Because I have tested it again and while you indeed can meet Shiba again, the dialogues is different. If you never help him, the producer introduces you to him instead.
He's in shopping mall the first time you go there. And is always there until 16th January. If you go to shopping mall (before 16th January) and don't find the scene in shopping mall, that means you already get the scene.
I have checked the code multiple times, and the thing you mentioned shouldn't happen.