Losing Control of Bestowed Enchantment Creatures
Your opponent never had control of Herald of Torment. When he took your creature, he only took the creature; he did not take control of any auras (or equipment) attached to it. So in this case, he would have control of a creature that has an aura that you control on it. This means that the creature would have +3/+3 and flying like usual; and YOU would lose 1 life per turn, not him.

So when the Bestow falls off and becomes a creature, it will be a creature under your control. It always was under your control.