What is the ruling on someone who finds a large sum of money in an ATM and is unable to return it to its owner despite repeated attempts with the bank, and what should they do with this money?

If it is highly probable that the amount belongs to a specific person and you have despaired of reaching them, then it must be announced for one lunar year in the place where it was found, in public gathering places, through media, and by contacting the bank. After the year has passed, the amount may be used, with the guarantee that it will be returned to its owner if they are found later.