I know I probably sound like a broken record but.... Dog's without solid obedience commands should not be off leash anytime! This includes dog parks or any other environment where other dogs or small children can be. My wish is that every dog owner would care enough for their dogs to have them properly trained. Sadly though this is not the case as you have found out. You are to be commended though for trying to warn the owner and for understanding your dogs personality enough to realize there was a potential for a problem. I wish more dog owners were like you.