Some money was mistakenly deposited into my account, but I decided to keep it anyways.
I'm not sure that's a good idea. Why did you keep money that you know is not yours?
I just assumed someone would come looking for it. I didn't think I would have to tell someone what happened.
You should not keep money that you know is not yours. Instead, you should return the money to the bank so they can place it in the correct account.
Nah, screw the bank. I'll keep it.
The person who that money belongs to will eventually contact the bank about their missing money. When that happens, they will be able to track it to your account. You can be in a lot of trouble if you decide to just keep that money.