I'm wondering why she didn't force the goblins to tell her or find a way to give him back his memories. Because all she'd have to do is threaten to leak it to the public and the goblins would have to be worried about the wizards carrying out a goblin genocide after the way they thought of Harry Potter.
Author's response
A good point, however there could be any number of ramifications with threatening the Goblins in such a manner. Do you really want to anger the people holding all you gold? ~EJ