I seen this on a Croation stream and you could clearly see the stewards pointing in the direction of the Cardiff fans when the object was passed to the ref.
I know above someone mentioned these are loyal fans and been to 7 aways but there are so many people who don't qualify buying tickets from mates or on social media (I can count at least 10 instances where I've seen HusddesfieId tickets for sale and the game has not sold out yet) that "nutters" are always going to get tickets.