The problem is most likely centered in the Evaporative Emissions System.
This is the apparatus that collects gas fumes from the tank, stores them temporarily in a carbon canister, and eventually routes them to the engine in order to be burned. However, when people have a habit of doing the “click-click-click” manuever with the gas filler nozzle in order to force more gas into the tank after the pump has clicked off, they wind up fouling the system by overfilling the tank, thus causing liquid gasoline to flow into the carbon canister. Once the carbon canister is saturated with gasoline, problems–such as yours–will take place.
Even if you have not forced more gas into the tank after the pump clicked off, it is possible that your son was in this habit. I guess that if I was about to cross the Atacama Desert, I might try to force as much gas into the tank as possible, but for the typical US driver with ready access to gas stations, this habit just makes no sense in the long run, as it can result in costly repairs. Replacing the carbon canister could cost a few hundred $$.
Also related to the Evap system is the possibility of (no, I am not kidding) spider nests inside the tubing of the evap system. For reasons that nobody can seem to figure out, Hyundais seem to be especially prone to the “spider syndrome”, which can also produce the symptoms that you described.
And, it is even possible that one of the evap system’s lines is kinked, or that the roll-over valve in the filler neck is in the wrong position. However, the one thing that you can rule out as a cause of this problem is driving through a large puddle. If there was water contaminating the gas, it would cause very rough engine operation and stalling, but would have no effect on the ability to put more gas into the tank.