I don't understand. Why would they have needed to enter the port? They should have dropped you off at the entrance of the port and you should have gotten onto the port shuttle buses (yes they take your luggage on the bus) with everyone else? And why did the police detain you? Clearly you did not do the driving?
But your point is well taken...check to make sure you are traveling with a reputable and licensed company.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013