I tested my rods on a road with trenches either side, looking for 'pipes', with a friend who could see down the trenches. Nothing, but at one spot they always crossed even with no pipes evident - eventually we noticed there was a wire running overhead at that point. Not saying it 'works', only - and most likely - that it sensitively discloses the operator's own subliminal suspicions/intuitions. Plus, confirmation bias - how many other trials have I not reported?
But in the bomb case, provided the bad guy thinks your fake detector works, you're half way there with all these credulous locals. Dice would be just as good, if he believed you were a wizard. All busted now, of course!