“ Additionally, since humans are intelligent they most likely would have fled to higher ground, swam and held on. Human corpses also bloat and therefore float on the water’s surface, that could be a very good reason why they were obviously not buried by sediment. Instead they rotted and decayed without fossilization. So we shouldn’t expect to find human (or even really hominid) fossils in sediment. ”
I guess that explains things like this?:
Leopards
In the 1970s Bob Brain came across the skull of an early hominid at the Swartkrans cave. The skull was identified as that of A.(Paranthropus) robustus, while the canine indentations on the pariental region were interpreted as those made by a leopard(Panthera pardus). The size of the tooth marks suggests that the leopard dragged the corpse carrying it by head.[5]The transportation of the kill through dragging is still observable in extant leopards. Therefore, since leopards are not scavengers, Brain(1981) concluded that the animal which dragged the corpse is the same animal which killed A .(Paranthropus) robustus[5].
http://en.citizendium.org/wiki/Early_Hominid_Predation
(early hominid fossils are commonly found with extinct animals like saber-toothed tigers)