You forgot to add the squadron of newer MiGs (including a variant which was not yet know to the Western World) burried just outside of the Baghdad airport where US troops had marched 3 months before their discovery. It took a windstorm to uncover one of the tail sections of one of the jets. Now imagine that most of the chemical weapons we are looking for can be stored in just a few tanker trucks. Much smaller than a MiG. And yet it took chance to discover the planes, it will take even more to find these chemicals. But, that's just one theory. Here's another by the UN.
An interesting development by the UN regarding WMD finds:
http://michnews.com/artman/publish/article_3985.shtml"The United Nations has determined that Saddam Hussein shipped weapons of mass destruction components as well as medium-range ballistic missles before, during and after the U.S.-led war against Iraq in 2003."