Theo didn't know that Draco was even really there, and he wasn't really seeing him either, but his body could feel his warmth and Theo moved a little closer to his friend by instinct. While Theo didn't have an alternative personality as such, he did suffer from dissociative tendencies; they had started out as his child mind's attempt to protect itself from what it was forced to experience and later used as a defense mechanism, a bolt hole for Theo's conscious mind when he needed one. If he was too overwhelmed by questions or prying, when he had to avoid being forced to remember or when he was faced with a situation he couldn't cope with, Theo would just shut himself down.
He'd escaped being questioned while he'd been at school, so it was only when he'd had a complete breakdown on the stand during his trial and then during his subsequent hospitalisation in the Janus Thickey ward that he'd started talking about himself in the third person. Sometimes Theo would describe some of the things he'd endured as a child - the Crucios, the physical damage, the punishments that took his tongue or fingers or toes - as though he'd watched them happening to someone else. Sometimes he'd describe the scene as though he was this other person watching it happen to him. The screams he'd hear coming from the wall were never his own, the things that had happened to him became something else, euphemised, all the desperate little methods Theo had developed as he'd grown to distance himself as far from the truth as possible.
So when Theo replied, 'he's not here, he's waiting in the cold, shivering in the cold' it wasn't really another person responding but then again it wasn't wholly Theo himself either. Draco moving to make the space safer for the sleeping-not-sleeping Theo really had him shivering as his body missed the heat of another person, even though Draco was still in catching distance.
Draco's tactics didn't seem like they were working as Theo stood where he was, quivering now and again and looking around like something afraid of being seen, but really Draco's conversation was sinking in somewhere in Theo's head. Enough that he flinched at the mention of the word 'home'. He'd started to track Draco's movements too, his head following the blond as he pushed boxes out of the way, nowhere near as observant as Theo usually was but more than completely detached from his surroundings.
"I... I'm sorry." he murmured, and that could have been a response to Draco or whatever Theo thought was happening in his dreams. "It's difficult. He always watches; the crows know when the best time is and it's never the same time." He looked up suddenly, fearful like some prey animal being dropped upon by a hawk. "Don't let your guard down." He warned, still watching the ceiling like it might fall in on him, his voice suddenly tearful.