Prevention includes practicing dropping high value treats near Bo when he is eating from a Kong. The idea is for Bo to associate the high value food with my approach towards him. When Bo goes for the high value treat, I pick-up the Kong and wait for him to finish the treat before handing the Kong back to him.
I try to do this exercise with Bo at least once a day. Today, while socializing Bo with two other dogs, I had the opportunity to give what we've been practicing a try. He found a peanut butter filled dog bone on the lawn where the dogs were playing. Bo took the bone and ran away from the other two dogs in an attempt to keep it for himself. Once the two dogs had stopped playing and chasing, Bo lied down with the bone. I approached him and dropped chicken jerky and sure enough he let the bone drop and let me pick it up. In this case, I didn't give the bone back to him but he was okay with it. He continued playing with the other dogs.
Here is a video of me practicing this very important skill with Bo at home with a Kong.