You apparently have not spent much time at ski resorts. The resort has no direct way of knowing who or what car "belongs" there. You can drive to the resort, park your car, buy a lift ticket (cash or credit card), get on the lift and go skiing. Which is apparently what this couple did. Unless you buy as season pass, the resort has no name or other id associated with a lift ticket. Nor do they have any direct way to tell which car in the lot belongs to which skier.

Lots of people visit ski areas and don't ski at all. They drive up, park, go to the bars and resturants, and drive off when they are done eating or drinking. Again, no direct way to tell who's car "belongs".

It is also worth noting that (in the US at least) a downhill resort has no responsibility for off area search and rescue. Even if a resort has gates to let you ski off area, once you go throught the gate you are responsible for your own safety. That being said, almost all areas will try to help skiers who get into trouble off area, but they are not required to do so.