What's weird about this is that employers will want to see an employment history and will contact your previous employers to confirm you worked in the role you stated, for the specified dates, and confirm the terms of your departure (layoff, quit, or fired with cause). I'm not sure how much else they're legally allowed to disclose - probably worth looking into!
I guess either the employee didn't list that job on their resume, or the new employer didn't follow up. Not listing a job will leave a large gap in your resume, and employers really don't like those.
IMO, they should've gone for a criminal prosecution. That amount of theft is way too big to overlook, and conviction would leave them with a criminal record. Employers usually do criminal background checks, which would turn up such a conviction.
Remember folks: the cost of theft is placed on the backs of everyone else. If you're honest, it's not in your interest to turn a blind eye to any kind of theft or fraud. If you're dishonest, no crime is harmless or else it wouldn't be a crime.