So technically the police can only prove that he did a dirty chat with another legally constenting adult which technically isn't solicitation of a minor.
or you know, intent to solicit explicit acts with an underage minor. Hey you slept with a 15 year old from a club. Guess what? still illegal even though she told you she was 18.
...also bullshit. You can't be expected to do a police database search on every hot chick you come across, although anyone who sleeps with someone without knowing them a little better than that is a raging, 5-alarm idiot.
You know, maybe people like that SHOULD go to jail, if only to knock some goddamned sense into them.