Is this reporter, who claims there were clothes in the bag, incorrect?:
http://www.local6.com/video/18265292/index.html
Also, they could be taking the vacuum cleaners to see if the soil where she was found was vacuumed up and in the vacuum, presumably AFTER Casey was arrested. In other words...if someone in the Anthony family MOVED the remains, they would have tracked the soil back into the house and, in the process of vacuuming, the matching soil would be in the vacuum.
I would think that over the course of 6 months, any paper in the bag, subjected to water, would be disintegrated.
By the way, there MUST have been something weighing the bag down or it would have floated to the top of the water and there would have been no indentation in the bottom of the ravine when it was found. Certainly, the weight of the corpse would have left an indentation of some sort, but if the area filled with water later, the body would have floated up to the top.