A year before an exit prob means they only vested like 25% percent of their options. At that stage they were prob pretty expensive options and highly diluted. Options are not much good if they are not vested and priced too high.
Typically when a company is acquired unvested employee options are converted into options in the acquiring company's stock. So in this example the employee in question would just have to work another three years to realize the gains (just as he would have had to do otherwise).