How can money taken unlawfully be returned if its owner lives in a distant country and cannot be reached?

You must repent to Allah Almighty for taking money without a legal right, feel remorse, and resolve not to return to it. One of the conditions of sincere repentance is to return the right to its owner. "The hand is responsible for what it took until it returns it"; otherwise, it will be a debt in the hereafter. You must take the initiative to return the right by any possible means, and if you fear exposure, then find a way to deliver the money without mentioning your name. If you are unable to return it, then give it as charity on his behalf, and if you find him later, give him the choice between approving the charity or taking his right.