Harry Potter Partway Thoughts - In the Tent

(Semi-spoiler alert. I've read up to page 286.) So who is the thief that Harry saw thru V, stealing something (a special wand?) from Gregorovich years ago, whom Harry recognizes but can't place. My hunch: it's the same guy that Harry saw in the photo of a teenage Dumbledore inside Rita Skeeter's book that he found in Umbridge's office. Harry didn't get a chance to read the caption, so we don't know who it was. Aberforth? Doge? Or a further stretch - Luna Lovegood's father? (Maybe what was stolen wasn't a wand, but the symbol that X was wearing around his neck at the wedding, the one that set off Viktor Krum.)