Officers say the item was dropped from Pier Road around 03:30 on Saturday 9 October.
“The vehicle is believed to have sustained damage as a result. The driver of the vehicle remains unidentified and is asked to contact Police,” they said.
Police are now appealing to anyone who knows more about the suspected “malicious damage” or who has dash-cam or CCTV footage of the area at the time.
Those who can help are asked to call 612612 or make an anonymous report via the Crimestoppers website.
