I understand the disappointment. It's not that you were hoping that he'd think of you at all, but the fact that he asked you and didn't follow up is very disappointing. But don't give up hope yet. Maybe he is planning something special for this weekend?
While the 'old' me would have probably gone out and gotten the present myself to "rub it into" H's face, I would not recommend to do that now. You might cause him to feel bad about it, especially on the off chance that he had a 'good' reason for not getting them yet. But as you suggested to saying 'what happened to my slippers?' in a jokingly/happy tone, that might be an option. Just try not to show your disappointment quite yet (both vocally and through facial expression).
