Swarming is as common if not more common than supercedure. They probably swarmed. Maybe they superceded. The paint sometimes wears off, but close inspection usually shows at least a little bit of paint around the edge of where the dot used to be.
The biggest myth about swarming is that putting supers on is all you need to do to prevent it.
That works well in the middle of summer, but is not adequate at all in the middle of spring.