There could be a quick end to this tale, depending on the intelligence of the parties involved. It's a policy of CEX, the second-hand store where one copy was purchased from, to require a valid photo ID when buying a game. If the thief in this case used their actual ID, the police will have a very simple job in identifying who was at fault. Additionally, the UK has very strict laws on handling stolen goods, and CEX itself may in trouble for not doing its due diligence (it doesn't seem to care, though). We've reached out to all parties involved for more information.
Keen-eyed among you may have noticed that this all seems to have happened on April 26th, which was once the release date for the game. Despite a criminal enquiry being opened, there's a possibility that this is not in fact a theft, and instead is an early shipment issue. For now, all we have to go on is Sony's word, but we'll update you on any developments to the story.
Source: Sony