The fireplace appears to always spawn, but the logs may not. If the logs do not spawn in the fireplace a player will not receive the shinbone. If this happens the player must reload the game by clicking Leave Game, then Resume Game. Can be found in Adventure Mode, which appears to have two fireplaces in 2.4.1. Bone was found in the lower fireplace near the entrance to the manor but may have been in both prior to the bone being taken. There will be a checkpoint that will allow a player to leave the game and rejoin it in the mansion to quickly farm the item.