A fake Facebook account was used to establish contact with the targets who were then asked to meet in Wolverhampton.
But after arriving at the designated trade point, the victims were confronted by two offenders who ambushed them and stole their vehicles.
Officers from West Midlands Police have now released an image of an additional suspect they are looking to trace in connection with their investigation.
A West Midlands Police spokesman said: "Following enquiries a 17-year-old boy was arrested on suspicion of robbery offences and charged. He appeared at court on Friday, January 22.
"A 16-year-old who was also arrested in connection with the robberies has been released on police bail pending further enquiries.
"Detectives have now released an image of an additional suspect, and are appealing for your help to identify them."
Anyone who recognises the individual are urged to call West Midlands Police on 101, quoting incident reference 20WV/317173E/20.