All the more reason to only use legally licensed and insured red plated taxis. As has been mentioned, Negril is a small town and the police pretty much know everybody.
Perhaps you dont know this person as well as the police do. Like it or not, you were involved in an illegal activity and you didnt go to jail. Count your blessings, and next time take a legal taxi. Had you been in a legal taxi, you would not have had to worry about being an accomplice to a crime.
If a legal taxi is carrying something illegal, all passengers are considered innocent. This is not the case when you are in a private passenger vehicle.