I am unable to reproduce the issue thus far using both slay and actually killing the mob.

*snip all the room info about said mob cause its in an area explore*

Gorgik paces angrily about, muttering a constant streak of curses.

slay gorgik
You slay him in cold blood!


exa corpse
A pile of fist-sized chunks and loose organs are all that remain of Gorgik's corpse.
The corpse of Gorgik contains:
a key made of ice

get key corpse
You get a key made of ice from the corpse of Gorgik.