aw man that's awful. Hopefully he does get training help and a walking tool to avoid falling over again. Bad timing, I know no matter how savy you are with dogs that if your attention is distracted at the second a dog suddenly just TAKES OFF you are in for a fall (no time to brace yourself) though regardless of walking tool. Rocket Dog fetching a toy is gonna be very very very high level distractions for many dogs especially if the owner didn't know it was coming (not that this was your fault in any way just reality that if a high level distraction pop up and you are unprepared it's going to require TONS of training to get a dog that would stop on vocal command alone - if you can even get a word out before they are gone!)
Good job Rocket Dog!