Having worked for said airline, the hang luggage size/weight has been an on going issue. The company is scared of upsetting it's pax (particularly it's gold card holders) and as such seem is very lenient with what is let on board. The numbers of gate staff has gradually reduced, so they (not all, some are very proactive) struggle to police what is coming on board. Many a time, the crew are left with numerous wheelie bags in the galley during boarding on the A320 family due to a lack of space. The procedure is for the dispatcher (TRM) to close the door, remove the airbridge, then reattach the airbridge and open the door to off load bags, this making it a handing delay. However, many a time, the airbridge doesn't come back.
I flew with American Eagle a couple of years ago, only the agent boarding the flight, yet she managed to check every passengers' item of hand luggage and tagged that was too big, impressive.
Another issue is 'hand baggage only' fares. So, pax bring on their worldly possessions, some of them look like buckaroo.
Then you have those who have connected off from a 747/777/A380 and think that their crate will fit into the locker of a A319.
I hope that the passenger recovered and I hope that the airline will finally start looking into more strict guidelines.