Oo I finally get to be helpful(?)I followed the walkthrough, but week after week, the Michelle toys scene just won't trigger.
I had the same problem, when I was strictly following the walkthrough. After you tell Michelle about the schoolgirl and plant the panties, you have to then knock on her door again a few days(?) later where you get a scene where she tells you she found out he's cheating etc. And then after that, the toys scene will appear.
Unless it was pure coincidence; I spent weeks in-game without it triggering, then I tried talking to her again, got the above scene, and the next night I got the toys scene first time.