He is embarrassed to return the money to his neighbour because it is such a small amount
Question

                When I was young, about 11 or 12 years old as I remember, I used to take public transportation to and from school. One day I found that I had lost my money and all I had left was not enough to pay my fare. I was 5 Egyptian pennies short of the fare, which is the smallest coin in Egyptian currency. A person who lived in my neighbourhood but whom I do not know personally and he does not know me gave me enough money to pay my fare and get home, and said I could pay him back later. Now a lot of time has passed but he has not come to take anything from me. Now I am 18 years old. Is this regarded as a debt that I must repay or not? Please note that I feel embarrassed to go to him and give him this money because it is such a small amount, after such a long time. May Allaah reward you with good.
Praise be to Allah.
    Usually when a person gives such a small amount of money he 
    gives it as a gift, not as a loan, which is why he did not come to take it 
    back. Perhaps he told you that he would come to take it back so that you 
    would not feel embarrassed, and so that you would take this money from him 
    and not refuse. You should respond to his kindness in like manner, and 
    reciprocate either by giving him a gift or making du’aa’ for him, etc. You 
    could also – so as to overcome the feelings of shyness  – go to him and 
    greet him with salaam and ask him how he is, and tell him that you have not 
    forgotten what he did for you in the past, and thank him for it; you can 
    tell him that you still owe him this money and that the only thing that kept 
    you from returning it was embarrassment. If he lets you off, then praise be 
    to Allaah, otherwise you can repay him. This is a kind of calling people to 
    Allaah, which lets you address the importance of people’s rights and paying 
    them off no matter how much they are.  

    And Allaah knows best. 

    May Allaah make you more keen to do good and more honest, and help you to do all that is good.