That's actually pretty common criminal activity in banking, where an employee will take money from accounts of clients and "gamble" it on high-return short term investments.

Obviously I won't be naming Banks here but what usually happens is:

1) If they succeed in their investment they put the money back and walk out rich. Their venture can be detected during an audit some time later but if there's no money missing the worst that will happen is that they will be fired because banks are very sensitive on their reputation and they don't want people to hear that its possible for a such thing to happen. They also don't want the insurance and other regulatory bodies to hear about this.

2) If they are caught before returning the money(this could be audit, customer complaint or a whistleblower) they will be given the option to return the money and get fired. If they can't return the money, then a formal investigation and criminal case is initiated.

3) If they lose their investment, they will flee and trigger an audit. They won't be able to resign and leave gracefully because the process of using this money involves periodically putting it back at strategic times to avoid trigger an audit due to discrepancies, therefore it's very risky to keep coming back to work if you don't have the ability to put the money back at short notice.

This is one of the reason for people in banking having mandatory 2 weeks time off at a time in many jurisdictions. Stealing needs maintenance and maintenance needs access.

I also wouldn't call it "repay his debt to society" because due to money that he stole, he made the public transport more expensive and housing less affordable.