when you create the enemies.. give em a skill
f.e.
#define id skill1
var ids_given = 1;
ent_create(blabla);
action enemy()
{
my.id = ids_given;
ids_given += 1;
[...]
//enemy death
killed_e[my.id] = 1;
}
and after level_load, when you readout the file.. just ask with a loop and ent_next for the entities *.id, if it´s the same as the i from the for loop.