Davis said that there were "two detonators and a box of C4 bricks" missing. However, in the previous shot, there were four detonators missing (unless they had used two and the other two were unaccounted for). The box of C4 was still there, although it was almost empty, with only two bricks left.
Moreover, if the bomber was going to detonate several blocks of C4, he would need a detonator for each, not just the two (or four) that were missing.