What is the ruling on taking a commission for a car sales intermediary, paid by the client, which was not disbursed to the intermediary due to difficulty in contacting him, knowing that it is unlikely he will claim it?

The company is permitted to add the broker's commission to the car's price and sell it at that price, as long as there is no falsehood or deception involved. As for the broker's commission that remained with the company, if you are responsible for it as an agent, it is a trust (amanah) that you are not allowed to dispose of. You must return it to the company if it is highly probable that the broker cannot be found and thus it is impossible to hand it over to him, based on the Prophet's (peace be upon him) saying: "The hand is responsible for what it has taken until it returns it." It is better to give it as charity on behalf of its owners while guaranteeing it.