The day Hermione had been captured, the day she had gone missing, was the day Hermione, Ron, and Harry had snuck into the Ministry looking for Umbridge. Mundungus Fletcher had told them about the locket but they had walked themselves into an ambush. The fight that followed resulted in the three splitting up and Hermione being captured by Lestrange, taken to his home. She didn’t think anyone even knew why the three of them had ended up at the Ministry. If they had, Hermione certainly wouldn’t have been shoved into the Lestrange dungeon to then come face to face with the very locket that was hanging around Sabine’s neck for safekeeping.  