What would you do?

Recently, an acquaintance of ours told us he found $1000 cash in an envelope in the parking lot of the grocery store where he works. Here's how the conversation went:

Brett: You're going to turn it in, aren't you?
Money Finder: No, why would I?
Brett: Because somebody lost that money and they are probably freaking out. They will probably give you a reward.
Money Finder: Why would I need a reward, I have all the money now.
Brett: Whatever, Dude, just do the right thing

So Brett got home and told me about the conversation. I sent a text to the money finder telling him that the right thing to do is turn in the money and how would he feel if his mom lost that money and nobody turned it in. He said that I would do the same thing if I was young like him. WRONG! It would never even occur to me to keep the money. I know how I would feel if I lost that kind of money, I would be sick to stomach and beside myself and I wouldn't want anyone to feel that way. I keep picturing a little old lady getting to the register to pay for her groceries and discovering she had lost her money. How sad! So my question to those that are seeing this, what would you do?