How is that not _exactly_ the case here? The company offers a $10k fee for referring an employee who stays 6 months. Employee refers someone who stays 6 months, but the company forgets to pay him and he forgets until a month after he quits. The company owes him $10k, and the fact that he quit is immaterial.

I don't think the naming and shaming was a very good idea, but he is absolutely owed $10k.