You have a good chance of them coming true if they are isolated from the others. If there have been a lot of flowers in between them, that helps too since the bee will visit more attractive flowers instead. 500 feet is the minimum recommended distance to ensure no cross pollination.
Pepper flowers are perfect meaning they have all the parts to make babies on their own so they do not need to be pollinated by another flower. So you only need to cover the blossoms to make sure cross pollination doesn't occur. You can put netting over the whole plant. Some people build little mesh cages to go over the plants.
Why you were not successful earlier, I do not know. It could of been the weather at the time.
Remy
