Am I sinful for not returning the extra piece of clothing that I took by mistake, and should I have donated its full value even though it was not worn and was donated after a long period?

The questioner committed two errors: The first is not returning the item to its owner, according to the hadith (definition): "The hand is responsible for what it has taken until it returns it." There is no obedience to the husband in disobeying the Creator. The second is donating the price of the item while its owner is known and it is possible to return it to him. It is not permissible to donate something on behalf of its owner unless it is impossible to return it to him, or to his heirs if he has passed away. What is required now is to seek the owner's approval for the charity. If he does not approve, then its value must be paid to him.