Partly inspired by the question about using Mending to reattach body parts to a corpse , this question concerns both the spells Raise Dead and Revivify, which both state that they return dead creatures to life, but (respectively):
This spell closes all mortal wounds, but it doesn’t restore missing body parts. (PHB, Raise dead)
This spell can’t return to life a creature that has died of old age, nor can it restore any missing body parts. (PHB, Revivify)
I started wondering what qualifies as "missing." It seemed clear to me that a character couldn't be Raised or Revivified if you had their decapitated body but no head (unless they could survive without it), but what if you had both? If a creature had its head cut off, and you placed that severed head on top of its body, wound to wound (presumably facing the correct direction), would Raise Dead or Revivify be able to bring them back to life, or would the head be considered "missing"?