"According to my records, the man named Hope Estheim went missing 169 years ago."
It was something he had once said, yet he hadn't remembered his own kidnapping.
In the new world, he had plenty of time to himself. Time to think. Time to remember. He remembered joining forces with Snow and Noel to help fix the world somehow, he remembered pushing Lightning to the back of his mind, putting the welfare of the world first before his feelings.
He remembered being haunted by her.
To say it was Lightning would be unfair to Lightning herself, seeing as she obviously had nothing to do with the rose-haired phantom he saw nearly every night for decades. Yet…he knew it had to do with Lightning. Everything had to do with Lightning. It didn't take long for him to become obsessed with the phantom, beckoning him into the crumbling Cocoon. It looked just light her, talked just like her, so it had to be her.
He just wanted her back.
Even after a few years in the New World, he never told Lightning about it.