I think they mean that his body was last seen then. Probably the date he was buried.
Yes, you may be right (as I noted in my post at #55). I guess I was figuring she wouldn’t stand out there with a sign for the media, if there wasn’t more to it than that, but you never know. Presumably now that she’s put the sign/name/date out there, some local journalists will try to track down other relatives for more info. Maybe none of them have been there since the funeral, and rushed out to check when they heard the news about the cemetery — not because they wanted to reassure themselves that he was still there, but because they were hoping he’d been dug up and discarded so they could have a shot at a cash settlement.