Anybody who says they never lost anything in the grass... you mean you never killed anybody near a slope and had the weapon go sliding off somewhere? What about killing a will-o-the-wisp, those things roll like an eighteen wheeler with a full tank of gas when you kill em and the yellowish bits hit the ground.
I've lost stuff in the grass many times. I recently killed a bandit and there was a sloped area on both sides with many trees and rocks and tall grass and I have no idea where the weapon went flying off to.
I play in 3rd person and usually you can spot the body or the weapon but sometimes it's pretty hard, especially if it's a small item like a dagger. I think I prefer that enemies drop things, rather than having it available in their inventory after death. It makes it more interesting to have to search for stuff but it can be annoying if it was a sword or something you wanted and it can't be seen. Maybe they'll have shorter grass in Skyrim or less dense grass or the grass will flatten out under the weight of bodies and heavier items.......... or maybe even some item detection spell like they have in the Finders Keepers mod which I've used before to detect stuff, especially arrows as I like to retrieve those when I can.
As for the vampire dust thing, maybe they should go poof like suggested when they die. Maybe when they die, the flesh turns to dust and their skeleton collapses in a heap.