Then, another thing to note: how can you know that a unit is been killed, if you never even have seen it? And how can you know that by just opening a save?
The answer is easy: the death of the unit must be a world event, an event which anyone can easily know because it's announced. A Great Person death. Which GP can die? Great Generals attached to units. Other GPersons, such GS, GE, GA or else can be killed if captured, but no world announcements in that case.
Thus we can expect a Rifle, Infantry, tank, MG, MI, MA attached to a GG in a 1-tile-island reachable only after Astro. I think we can discard armored units, so it will be a GP unit or an MG. But, as i have tested, MGs are too easy to kill for cuirassiers, so i think a GP unit.