I borrowed-or I thought I borrowed 3 Dollars from my father's wallet while he was sleep. My father was sick for almost 2years and usually didn't get that much of sleep unless he was under medication. Anyway, this was the first time I saw him sleeping peacefully, so I didn't wake him up and I wanted to borrow 3 Dollars for gas. My intentions at that time was to put the money back when I came back from my work and hopefully tell him what I did. Sadly, I forgot that day to return the money and my father (Allah ya raxma) died a few months after. I don't know how one can repay the money he/she owes to someone who has passed away? I told this to people I know and they told me this is like stealing and there is nothing I can do in this world? I'm so worried, since I never stole any money and I really do want to pay back in anyway I can? Can you tell me please what to do?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

May Allah bless you for your devotion and May He Shower your parents with His Mercy.
You have to pay the three Dollars to the heirs and you have to divide such money according each one's share in Sharia. You are one of the heirs, so you may take your share from that money according to your legal share in the inheritance.
Allah knows best.