My ex would screenshot accounts of women from Instagram that he wanted to remember .. even saving some of their IG handles into his notes LOL.This behavior drove me absolutely insane which eventually lead me to looking into his messages and finding out he was cheating. He most likely saved that picture of your friend in the bathing suit to masturbate to.. why else would he have it? You're not stupid. Once they start doing this suspicious behavior it really destroys all trust. I really hope you do what's right for your soul.. I wish I had the courage looking back to end it the first time I caught him disrespecting me and thinking nothing of it. That was definitely one of my biggest regrets. I wish you all the best girl <3