That's exactly what happened. From what they told me "Legit just did the (nauwty wouwd) tutorial, it was like 3 AM, so I got off and got back on in the afternoon and it said my account was banned. And its my gamertag that got banned, not just the account.
They said it was for illicit activity and left the ticket open"
Anyone got a damn clue? (Also they don't remember their username this was a year ago)