Gilderoy Lockhart couldn't remember much beyond how to read or speak. Not even his name. He was taken to St. Mungos where many experts attempted to salvage what they could but all said the erasure was done by a master whoever did it.
On the bright side he was still rather high functioning and managed to relearn many mundane spells within a few minutes. Due to his lack of memories he ended up basing his personality off of his books. He found it weird how the books failed to awaken any memories but he continued to emulate the Lockhart of the books the best he could.
He was released after a few months when he decided to go on a trip to follow the path of his old journeys in an attempt to remember something. He traveled far and wide meeting many from his books, who didn’t seem to remember him for some reason, and learned many obscure forms of magic. When he met someone that played a large part in his stories, he would give them some of the money he made from that book, believing it to be what the Lockhart from the books would do. He even accomplished a few more adventures that he would eventually publish as new stories.
He eventually returned to Britain after years abroad when he heard the Dark Lord Voldemort had returned. As the great Gilderoy Lockhart he knew it was his responsibility to stand against evil as an honorary member of the “Dark Force Defence League”. Their battle was fierce and he even lost his dominant arm, but he succeeded in vanquishing Voldemort. He wanted to write about his new tales abroad as well as his defeat of Voldemort but he was missing his dominant arm, so he hired a scribe. She had wonderful handwriting, beautiful blue eyes, hair as dark as midnight, and she always wore a splendid gold necklace. Her name was Emily Riddle. She was the only scribe he tried that didn’t shudder at the name Voldemort. In fact, she would giggle and her eyes would gain this gleam as if she heard a joke whenever the name came up.
Over the course of their contract they fell in love and eventually married. Going on a few more adventures around the world, uncovering lost magic, before settling down and living off the money made from their books. A few years into retirement, Emily would go on to teach DADA at Hogwarts something she admitted she always wanted to do much to their children’s collective horror.