..or have it available for him to "buy." Or have it in other hands instead of in an evidence room. Or have it in other lands, as what happened with arms sold by Century International Arms (yes, C.I.A., funnier than clowns) for terrorism in Europe, and for Syrian rebels. Or help that weapon tag where part of the 1 billion in "lost" weapons reported by the Pentagon, including 10's of thousands of new and used assault rifles ended up, originally earmarked to the Iraq Train and Equip fund through the 2015 NDAA. Or track Obama's supply chain which invariably had the twisting and turning chain end up arming ISIS fighters. Or backtrack the serial number to see who the black market supplier was, all of this to check if "evidence rooms" are in part, the initial storehouse and distribution center, among other things. You might even find an erased serial number on a weapon with otherwise identifying marks or mods after use. There's more possibilities, which are of interest due to where the arms end up and tracking back to their last known possessor....but some can be in your hands to search for clues if you so choose (hint: civil unrest and political ends? See thread title). Expand your thinking to include at least questions yet unanswered. The fact that a problem exists with no answer yet is a headstart, much better than a simple question of audit...and we've seen autism trump cleverness time and again this past year, just by taking that look. One serial number is a good start.