The States police say that two girls – believed to be aged between 16 and 18 – assaulted the 55-year-old man and tried to steal money from him.
One was wearing a mask popularised by the film series Scream, the force said in a statement on Tuesday.
A 17-year-old girl was arrested and later released on bail.
Anyone with information about the incident, which allegedly happened between 10.45 pm and 11 pm on Sunday in the first lay-by on Victoria Avenue, is being asked to phone the States police on 612612 or Crimestoppers on 0800 555 111.
