If you’re at all like me, every so often you’ve watched coverage at the time or a documentary later about some great disaster, one that has taken many lives in horrific circumstances. You might have wondered — I have, anyway — about how or whether families and friends ever found out what happened to some of the victims. If you think of Hiroshima, or the tsunami of March 11, 2011, or even the events of September 11, 2001, you suspect — no, know — that there are people who died whose fates will be forever unknown to anyone this side of the Pearly Gates.