Which wand had actually killed his sister...his or Grindewald’s. He never looked to find out, was scared to.
IMHO, that seems more likely than seeing his family whole again. But if that's what Dumbledore were to look for, he would find it. Remember what Dumbledore said about the mirror--how it imparts neither knowledge nor truth. He could be 'vindicated' by the mirror, but it would be a false vindication.