I've definitely had the checkerboard thing on a few of my boarding passes in the past but I've never been thoroughly screened, but there's usually already 3 or 4 other carry ons they're already digging into so maybe it's not worth it for them, especially since I follow all the rules to make sure I don't get stopped for any useless reason. Don't know how credible that is that being said, but next time I fly I will check for that or the "s"