Sounds like they were just detained, not actually prosecuted.
Based on the context I suspect their "crime" was just as much being from the "wrong" part of Russia and the message being sent is "nobody from where you're from should be talking to ISIS, we don't care if you're undermining them" and they made them spend a night in a holding cell as a warning to everyone else.
Based on the context I suspect their "crime" was just as much being from the "wrong" part of Russia and the message being sent is "nobody from where you're from should be talking to ISIS, we don't care if you're undermining them" and they made them spend a night in a holding cell as a warning to everyone else.