A large amount of money came into his account and he spent it
Question

                Twelve years ago I found a large amount of money in my account, and I was in need of it so I spent it. I did not know who had deposited it in my account. We checked with the bank, and they could not find out the name of the depositor; all they were able to find out was the location where the deposit had been made. 

Now I want to settle the matter so that I will not be accountable for it; can I give it to charity with the intention of the reward going to the person who deposited it? May Allaah reward you with good.
Praise be to Allah.
    The arrival of this money in your account may have been a 
    mistake or it may have been deliberate. If it was deliberate -- which is 
    unlikely -- then it is money that the owner did not want and he gave it to 
    you, so you are entitled to take it. If it was a mistake, which is what 
    seems to be the case, then it must be returned to its owner. If it is not 
    possible to find out who the owner is, then you should give it in charity on 
    his behalf, on the basis that if you find out someday who the owner is, you 
    will give him the choice between approving of that charity or taking the 
    money. 

    Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) 
    said: 

    If he has money and does not know who its owner is, such as 
    one who seized it by force and has repented, or one who betrayed another and 
    has repented, or one who dealt in riba and has repented, and so on, who now 
    have money in their possession which does not belong to them and do not know 
    who it belongs to, then he may dispose of it by giving it to the needy and 
    spending it in the interests of Muslims. Al-Fataawa al-Kubra 
    (4/220), 

    And he (may Allaah have mercy on him) was asked about 
    pilgrims who encountered some Bedouin who had raided some people on the road 
    and taken their fabric; the bandits fled and left behind their camels and 
    the fabric. Is it permissible to take the camels that belong to the thieves 
    and the fabric that they stole, or not? 

    He replied: 
Whatever they took of people’s wealth 
    must be returned to them if possible. This is like lost property which 
    should be announced for the year. If its owner comes, all well and good, 
    otherwise the finder may spend it on the condition that he guarantee (to 
    replace it or compensate the owner if he shows up). 
    
    If there is no hope of finding the owner, then he should give 
    it in charity and spend it on the interests of the Muslims. 

    The same applies to any property whose owner is not known, 
    such as property that was seized by force, borrowed items, items left in 
    trust with another, and stolen wealth seized from thieves or lost property 
    that is found. All of this should be given in charity or spent on the 
    interests of the Muslims. Majmoo’ al-Fataawa (30/413) 

    And Allaah knows best.