Bullshooter- Two things to try.
1. Try putting a small length of surgical tubing over the end of the trolling snap that clinches down on the cable. Glue it on. The rubber will help it "stick" to the cable better, also stops vertical movement.
2. The other thing is to use a 1 foot diameter loop of parachute cord attached to your DR ball's hook eye. Then attach the trolling snap to the cord. The only way you'll lose it then is if you lose your ball altogether.