There were missing textures because the game was no where near being done. There were missing models because they had changed the file format and half the stuff was out of date. Same with the maps. Many were there but couldn't be loaded because they were an older version.
Edit: oh and there were tons of file dates ranging from over a year old to around 9/18/03. If they actually bothered to "fake" the file dates, they went through a LOT of work to make them different and from different times. The leak was definitely from mid September. Plus if he could get the Ritual and TRS versions of Condition Zero (the Ritual one was completed in early to mid August) then he obviously had access to their files at LEAST after August, way after E3.