Loot disappeared from Kael'thas The Eye

Loot from the Kael’thas Sunstrider encounter in The Eye disappeared a few seconds after opening the loot window.

I got Mind Controlled and died on the first pull and I did not check the loot during that pull. On my second pull and successful kill I checked the loot after the 7 weapons which spawn during the encounter and the loot disappeared before I finished reading the descriptions of all 7 weapons. After killing Kael’thas I opened his loot window and started scrolling down and it disappeared before I made it to the bottom.

I killed the other 3 bosses in the instance and they did not repeat this behavior that I noticed.

Nothing was mailed to me and at least one item I saw on the body is not in my inventory so I am certain it was not auto looted.

The weapons that spawn in phase 2 of the Kael fight aren’t actually loot. They’re temporary weapons to counter certain mechanics in P3. They’re supposed to despawn. You don’t get to keep more than half a dozen legendary weapons.

Kael’thas’ actual loot is on his corpse after the fight is done. If the contents of his loot window behaved the way you described, it almost sounds like you auto-looted and didn’t check your bags.