We visited the island last week-we found onlt 1 garbage can to dispose of our sandwich wrappers, and was yelled at for using it by a food vendor, we could hear her foul language yelling at us even after we walked away- way to treat a visitor!!!
Not sure where you stayed but in the past year or two there have been a lot of trash cans placed around Caye Caulker that are emptied by the village council. They may not look like the cans you're used to at home. They are big blue barrels affixed to heavy tires as a base and they tilt to empty. You may have put your trash in the vendor's can that they use for their business. Trash is a bit of a sensitive issue because whenever someone supplies a trash can for semi-public use (like the village barrels which are for pedestrians like yourself who want to dispose of bottles or wrappers), it gets abused by people who pack all their household trash in to it. You need to pay for every bag of trash you bring to the station so people who are not vigilant end up paying for a whole lot of other people's garbage. The vendor probably only wanted trash from their own business thrown in theirs.
You can still be mad if you want but that's the back story.