Amethyst by Helen Hardt

His best friend disappeared before he could profess his love. Her return is a miracle…but she’s damaged from her experience, and he’s engaged to someone else.

I’ll find her. I will find her if it’s the last thing I do.
Years ago, on a magical prom night that held promises of forever, Max Robinson planned to confess his feelings to his best friend and secret crush, Jenna Holland. But before he could utter the words he practiced countless times, Jenna disappeared.
Max was determined to find her, and he tried, but his efforts proved unsuccessful. He eventually moved on with college, a career, and an engagement to a woman who adores him.
Jenna has only blurred memories of being abducted on the day of her high school prom, but she has vivid recollections of the horrors and abuse she endured while held captive. She needs to reclaim her life, but the one person who can help her is no longer hers.