How hard is it to keep track of exhibits in murder cases?

The CAAF Daily Journal provides another example in a long history of N-M murder cases where the government can't seem to keep track of their own evidence. This case would be the recent murder case of U.S. v. Fuhrman, a not so nice chapter in the history of U.S. - Korean relations. Combine this with the recent decision in U.S. v. Quintanilla, where the trial counsel stole the murder weapon, and I think someone needs some remedial courses on evidence custody. Isn't keeping the evidence the surest way to guarantee a conviction stands even if the accused wins his appeals? If anyone knows, and can divulge the answer without having to kill me, I would be interested to know if Prosecution Exhibits 22 and 23 are actual exhibits and what they are, other than missing, because the court below referred to them only as potentially classified exhibits held in the WNYD SCIF (and some other not so descriptive words about how the documents were sezied).