I imagine that UNEB makes lists of schools and the respective papers to be done in each of the schools. The packing of papers ought to be done accordingly. Once the papers are counted and packed, then there ought to be a delivery note to each of the stations UNEB delivers papers. The delivered papers ought then to be cross checked according to the delivery note.
Now, how come examination papers can be missing and it is only realized at a time when papers are to be picked for children to sit for the exam?