Sainsbury’s complaint: Stolen bike on 100322

Hi
We live in SL3 8HR and my son goes to Upton Grammar School who is studying in year9.
On 10th of march 2022, he visited your store sainsburrys(SL1 1SU) along with his friends to buy some juice and he was there for 7 to 8 minutes. He parked his bike at bike parking in the store, when he returns he was not able to find his bike. Someone stolen his bike, when we ask the security guard there was no proper response. They are saying the cctv cameras are not working which are there. We wanted to to meet the manager, but they said he was in meeting.
We couldn’t able to control my as he was literally crying as it is new for his birthday and rode for just 3 days.
We complained to police online, obviously they ask for the evidence which can only given by sainsburys.
Could you please kindly help us in this case.

Awaiting for your response.