It would be if they were actually checking all 80m and only 9k were unaccounted for, but that isn’t quite what is happening. that is 9000 out of a sample of 18000 total which is half of them, 50%, which is not quite such a low rate. must be referencing something else, maybe used in a crime but unrecovered?
i want to imagine improvised zip guns and ray guns from the future, etc. but the reality is probably less exciting. 
maybe they don’t know which type of gun was used because it wasn’t recovered or recorded or?
