i dont think syria got as many as people think...the bulk will still be found in Iraq.
It is a very dangerous thing to transport chemical weapons, especially warheads in missles, small rockets, and mortar shells. one accident along the way, and its good by transport people. That, and they are so vulnerable to air attacks and such: not only an explosive hazard, but just nick one shell of sarin and its all over but the crying. That, and the fact that the Over head J-STARS aircraft didnt detect large runs to the syrian border that didnt get by without some kind of look tells me that the majority of what they seek is still in Iraq.
Its there. Under that sand pile somewhere.