The irony of all this is that I've heard stories of a few people who are on the naughty ban list that have managed to get tickets by being guests of season ticket holders
Ah, that's exactly how they found out. I've heard of people getting bans from Twitter because they've used their real name...
The other way that just occurred to me (you can tell I'm avoiding doing my actual job here!) is that the person who bought the ticket is someone from the club looking out for people exchanging tickets.
Unless when OP contacted the club they flagged his account as a potential wrong 'un and watched to see where his ticket ended up before hitting the ban button.