The incident happened at around 4.45 pm near the back entrance of Waitrose on Plat Douet Road, with police currently seeking witnesses.
The male suspect is thought to be about 15-years-old and has been described as having tanned skin, short brown hair and around 5-ft 5-in tall.
He was wearing grey jogging bottoms and a red long-sleeved hoodie. The victim – who was described by police as a young woman – was uninjured in the incident.
Anyone with any information, or who may have seen someone acting suspiciously in the area, is asked to contact States police on 612612 or Crimestoppers anonymously on 0800 555111.
