Because no one is supposed to touch or move evidence around, even if it's been outside in the elements. Police need to see where it originally was, whether it was sunk in the mud or on top of the ground. And having it in the original position can help them look for other evidence. Once you move something it is tainted, and while the Laundries may be upset, I'm sure someone has told them to call police if they found something. I'm speechless about their search and carrying a bag around for 30 minutes. I tell you, today has really been a whole new level of strange.