Okay, so I am just dying to know what loot can be found on their bodies:

1. Yamarz
He was supposed to defeat a giant. The giant hauled back, stepped forward with a mighty swing and... I swear to Malacath, Yamarz flew up into the air vertically and I did not see him fall back down. Now I can't loot him and the curiosity is eating away.

2. Alduin
When I slayed Alduin I noticed that his corpse was lootable for a short time during his death animation. But I wanted to see his death and missed out when his body vanished. What loot could have been found on Alduin during that short window?

Full set of Orcish armor. Nothing special beyond that.

you are unable to loot alduin

There is nothing on Alduin.