How can the right of a stolen phone be returned after repentance, and what is the best way to estimate its value after ten years?

Returning what is due to its owners is part of a complete repentance. It is not necessary to inform the friend about the theft; rather, it suffices to return the right subtly. Since the stolen item (the phone) has been sold, the thief must pay the value of the phone on the day of the theft, in the currency of the country where the theft occurred. It is also recommended to increase acts of obedience.