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This doesn't seem to apply with non living containers such as Chests and Wardrobes rather it applys with something that was alive and that you killed. If you save before an encounter with a conjurer/necromancer kill him/her loot body somehow die or reload and kill the same person again their inventory has been known to change.

This is true with dragons sometimes they won't have a lot of scales/bones to give you but reload and kill the same thing again and you can get more from that dragon.

This is something to concider when farming Human hearts. I actually got a human heart off of a dead nord, more specifically a Servant of the Falmer in Blackreach ((where the crimson nirnroot grows and you find the skeleton remains of Sinderion)) There is a large, well preserved underground city there where the Servants of the Falmer ((all human that I have seen)) And one dropped for me a human heart while one of the falmer dropped human flesh, these two are extremely rare ingredients ((never mind black soul gems and deadra hearts)) So it might be good to use/test.