Stuff you had in your inventory and then dropped becomes permanent and does not get cleaned up after 72 game hours. Things you place in "unsafe" chests will disappear when the chest itself is remade on cell reset, so be careful about being tidy.
The problem with dropping havoked items on the ground, especially in areas where NPC's move around, is that they can be knocked into inaccessible locations, or even through walls or the ground, and lost from player reach. I have a ring on the floor in the Skingrad house that's under a chair, so I can see it, but can't pick it up. That's double-annoying, because the only character that could have knocked it there is the player!
the ring should be moveable with telekinetic if you can see it, if not the small fireball spell is will throw it out (save before casting as it will probably end up a harder to get place.
And yes if you pick up something in a dungeon and drop it, it will not go away, typically you loot a dungeon and drop of the low quality stuff as you find more valuable items, a month later you revisit and the old items is still on the ground.
However I did not know that the cloud ruler temple was changed, yes I know they add a table and something but thought it was the same process as then you buy furniture.