Bicycle detail

sons bike was stolen from inside Lucky Store. There are surveillance cameras and a security guard who witnessed the incident from the minute my son entered the store with his bike. The guard gave a full description of the suspect and confirmed that the young adult was a local which should be in the police report. My son was out bike riding with friends and needed to use the restroom but had no lock to secure his bike. He went to Lucky and asked a random employee if he could bring his bike in while he used the mens room. He was told yes and within 5 minutes the bike was taken. I went to the store with the local police the next day to view the tapes and to file a report. The value of the bike makes this crime Felony Grand Theft. Or is the Security Agency liable. The guard watched the incident and did nothing to stop the theft from taking place.