If the weather is cold (as it was) the meat will freeze and/or can be dried quickly and be preserved over the course of the winter. Modern subsistence hunters

If the weather is cold (as it was) the meat will freeze and/or can be dried quickly and be preserved over the course of the winter. Modern subsistence hunters still do this. Hunt a large animal or two at the start of winter and the meat can be frozen and then cooked all through the winter. A couple of Moose for example in modern times could provide 1000lbs of stored frozen meat for a family to get through the winter. I am not necessarily saying that this would make it make sense for a tribe to bring down a dangerous 7000lb rhino and try to preserve it that way, but if the weather was cold during this period in Siberia it would have been possible.