If he hit Yes, the Vita would reformat itself into a developer unit. It would become a god among handhelds, immune to the digital apocalypse coming for the retail models. But if the serial check had been wrong, it would brick the device forever, turning a piece of history into a paperweight.
How to Check Go to product viewer dialog for this item. Serial Number: Exclusive Guide for Collectors Finding and verifying a PlayStation Vita check ps vita serial number exclusive
Do not use generic "serial number lookup" sites. They don't work for Vitas. Use: If he hit Yes, the Vita would reformat