What should I do with the gold necklace I found after one of the heirs paid its price to me from his zakat, considering me an indebted person? Should I give it to the heirs, or to the one who paid its price, or keep it for myself to pay off my debt?

If the deposited item is damaged without transgression or negligence on the part of the trustee, he is not liable for it; because he is a trustee, and the rule is that a trustee is not liable for what is damaged under his care unless there is transgression or negligence. So, if the zakat (definition) contract is damaged, and the trustee did not transgress or neglect, then there is no blame on him, and the payer should reclaim his money from the heirs to disburse it as zakat. However, if he transgressed or neglected, he is liable for the contract with a similar item or its value, and he is then permitted to take the zakat. If the contract is found later, it must be returned to the heirs, and the payer must reclaim the money and re-disburse it as zakat.