Frenzied: No Loot Mystery

[Seungkyu]

I recall back on live I was the designated group looter and I locked the Frenzied Ghoul's corpse before it even hit the floor.
I think I got some coin but I specifically remember it having no FBSS OR Manastone Ring.

This was before they added a loot message, so I had to deal with accusations of being a ninja looter and people screaming that I stole an FBSS.
Which is stupid because I had manastone rings in my inventory, if I was really committed to stealing I could have just said another manastone ring dropped and none would be the wiser.

I've never heard of this happening to anyone else or seeing it happen since. Has this happened to anyone else where they loot a named mob with "guaranteed loot" to have it drop nothing?
What could have caused this to happen?