Draco waited an entire day to ask Hermione whether she tracked her husband or not. Maybe he hoped if he was patient enough she would confess on her own. She didn't. They'd already established that what happened outside of his flat was off-limits to discussion. She wasn't allowed to ask him where he went on his mysterious missions and he wasn't allowed to ask her where she disappeared to when she thought he was asleep. It was an arrangement that was destined to fail at some point.