Do you work on recalls while in the dog park? I worked w/ a trainer years ago who talked about how people take their dogs to the dog park and don't ever ask for anything in return for this glorious reward. So outside the gate, you ask for sit, down, focus, etc. Reward with treats! Go inside the first gate, do the same--get the dog's focus on you. Then go inside the main gate (and NOT when other dogs are crowded around--not allowed and certainly not safe), ask for a sit and focus on you, then release the dog to play. Back when I used to go to dog parks (and I don't anymore, for the same reasons others here don't like them), I would call my dog to me periodically during play, grab her collar and give it a light shake, praise and give her several treats, and then let her go again. I saw it too that dogs would run away when the owner called them--well why not?! They are having fun, and coming to the owner means that the fun ends, so why would they want to come back? So you could try doing recalls (like every couple minutes while you are there, at least at first), grab the collar, praise and treat, and let the dog go again. Make it a BIG reward for the dog to break away from play and come to you, and soon recalls at the dog park are no longer an issue. Even my basenjis had good recalls at the dog park.