Do I bear a sin, and what should I do, if I found a gold piece in a mall, reported it to security, and no one inquired about it, then I disposed of it before a year passed after estimating its price and weight, and no one has inquired about it to this day, after more than a year has passed?

It is not permissible for the finder to dispose of a found item before publicizing it for one lunar year in places where its owner is likely to be found, and through modern advertising methods. If the owner comes and identifies it, it must be handed over to him, based on the Prophet's (peace be upon him) saying: "Recognize its binding and its container, then publicize it for a year. If it is not identified, then spend it and let it be a trust with you. If its seeker comes one day, hand it over to him." Whoever sells a found item before a year has passed has done wrong and is liable for it. He must pay its owner its equivalent if it was raw gold or silver, or its value if it was jewelry.