Police are looking for whoever used a rock to smash the driver's side window of a parked green Land Rover at West Park.
It happened in the public car park next to West Park Apartments on St Aubin's Inner Road sometime between 4:30pm on Sunday 20 September and 8:40pm yesterday morning (Tuesday 22 September).
A cap and set of keys were stolen and officers think the ignition was also tampered with.
It's being investigated as an incident of malicious damage.
Anyone who saw anyone acting suspiciously between the above times, or with any other relevant information, is asked to call police on 612612 or Crimestoppers anonymously on 0800 555 111.