I would call that car stolen regardless if the person it was stolen from is alive.
Of course, a stolen car is a stolen car. And stealing it in the first place was unjust. If we can correct this injustice by having the thief return the car to its original owner and return the money to the good faith buyer, then all is well. But sadly it is not possible to correct all past injustices without adding further injustice. Two wrongs don't make a right.
What alternative would you suggest?
Transitioning into collaborative ownership (which would benefit all people involved) it would be a non-violent means of doing so as people would voluntarily do this based on the benefits.
Then maybe there is a future where these terms of 'ownership' would no longer serve us. I'm speaking philosophically with my ethics (the future I see) I realize this isn't done in one step. It's a process. So, collaborative ownership of all private property (i.e. commons) would be my alternative, thus removing any sole private ownership. The car example is poor, I'm referring to the commons where a vehicle would be personal (with added taxes from Commons used resources, but that is another topic.)
As long as it would be on a voluntary basis, I have no problem with communities trying this idea out. No doubt, in a free world, where all human interaction is voluntary, different groups of people will live different kinds of lives with different rules and practices. It is an empirical question which rules of ownership benefits people the most, and I support the practical experimentation with different rules.
However, my prediction is that even though collaborative ownership might work in small enough groups, it will break down when groups grow bigger.
This is exactly the future I hope to help create. One where there is as diverse a system of relating as there are people to relate! That each one is tailored to it's participants! This is possible, and practical!
That's just it, with decentralized governance models they don't have to grow bigger! We can fractal this model on any growth scale and the division of collaborative ownership will never exceed roughly 150 people before it fractals out. As roughly 150 is what has been called an optimal number of people to interrelate. It's about as many people as we can recall names, information, relationships about.