There is no solid proof they were destroyed. An Israeli intel chief and one of Saddam's own generals claims the bulk were transferred from Iraq to Syria. Nobody knows for sure. But stockpiles of WMDs were found. Even the NY Slimes admitted as much.
On CNN I saw missiles being moved into Syria from Iraq. I only saw the satellite shots maybe 2 times and they were removed from the air. They were on Russian trucks and draped with cloth but it was apparent what they were.