He was actually let go by the company initially before the IPO. They then decided they needed him for it and beyond, so they talked him into returning to the company after he'd been gone less than a week. He didn't have another job lined up, and enjoyed the work, so he was happy to go back.
At the IPO, less than a month later, they decided to give stock and stock options to all staff who had been with the company for more than a year - increasing amounts based on longevity. He'd been with them for 10 years - but they decided that since he was let go and re-hired, they were only counting him as having been there for the month since his return and he got no credit for his previous 10 years.
So co-workers who'd been there essentially the same time as him were paying off houses, buying new cars, and taking trips to Hawaii. And he got nothing.