Heh, I vaguely remember Professor Jones sending some of his supposedly incendiary red and grey chips to somebody else to independently test, and the guy reported back that he found them inactive, and speculated that something had happened to them in transit.
ETA:
Found it. A Frédéric Henry-Couannier tested the chips and could not get them to ignite. He speculated that either they had already been ignited or that his sample had been "deactivated to prevent my independent corroboration of a crucial proof."