"He had messaged me several times before that," Kohn told the website BuzzFeed. "I never replied."
The X-rated photograph was sent to her via Instagram, which Ryan could've only found on her Tinder profile.
His account on the photo-sharing service contained his full name. Although, since Kohn's actions went viral, his profile is now blank.
Using that and his location, she tracked down Ryan's Facebook and with some "stalking", located his mother.
"I tried to be civil when I wrote the message to the [mother]," Kohn said.
In the message, which included a screenshot of the surprise crotch selfie, she wrote: "I have never talked to or met [your son] but he has sent me this picture. Can you please tell him not to send unsolicited pictures to women?"
A day later, she received a reply - an apology in English and Spanish from the shocked mum, promising to speak to Ryan.
"She took it pretty well," Kohn said. "She wasn't turning around and attacking me. It was super nice."
But Ryan is furious. While not admitting the penis in question was his, he told BuzzFeed it was a private picture.
"If that was 'me' what she did was illegal. You can't share those types of 'private' pics without consent. I am not sure if you are aware of that."
It's not clear if Ryan saw the irony in his defence.
Still, it's a cautionary tale about the importance of keeping your nasty stuff to yourself if no one wants to see it.
"I'm not the first person to receive things like that and it's not been the first time," Kohn said.
"I'm just tired of people in general thinking they can send things like that without repercussions, and they think it's okay."
