Mobs don't seem to attack the corpse, I died a few times to mobs and they left it alone. I took a look in the config and the only option on is damaged by weapons, so I'm not even sure they could hurt them if they tried. Also it looks like if you break a corpse with items in it, the items pop out, so at worst our items should still be hanging around the place we died as usual. I think what might be happening is the corpses are just falling through the world, some people say they find them in caves below where they died, others that they lose their stuff more often around bedrock, so I'm guessing they are sometimes spawning "in the ground" and falling through the world until they hit an opening with a platform to land on, or just falling into the void if they don't hit one. Or they just look for an open are below to spawn in, and don't exclude the void.
Edit: Also it looks like corpses sometimes spawn invisible or something and might show up if you reload the game. I died while building part of my base yesterday and couldn't find the corpse anywhere, I loaded up the game today and the corpse was just sitting in the middle of the floor in an area I couldn't have possibly missed.