How can one recover his gold mortgaged to his friend who claimed it was lost, knowing that there is no written mortgage contract, and is it permissible to defame him in the market by saying, "So-and-so is a thief and a betrayer of trust"?

Pledged gold is a trust held by the mortgagee. The mortgagee is not liable for it unless he is negligent in its preservation or infringes upon it. If the gold is lost without negligence on the part of the mortgagee, he is not liable. However, if he is negligent, he is liable for it. If his negligence is proven, he should be approached courteously. If he does not respond, seek assistance from someone who can influence him. Otherwise, you may lodge a complaint with the relevant authorities to reclaim your rights, but you are not permitted to strike him. It is permissible to warn people about him if his negligence and procrastination in fulfilling the right are proven and you fear for them because of him.