At first I was really surprised this could happen at LAX as the airport has a policy of using an airport security car to watch the wingtip on every A380 when they taxi, but the article states this occurred as one was towed empty from the mx area to the gate. In this case a car would not have been present since the aircraft had not even made it onto a taxiway and would presumably have been monitored by ground personnel acting as "Wing walkers".
In this case somebody was clearly asleep at the switch.