This is why most buildings (or it could be a bylaw, not sure) do not allow pets to be on the baclony alone or at all.

Too many have fallen to their deaths and too many have been hung by their leash for the world to see.

I dont allow any of my dogs or the cat on the balcony. I know i wouldnt be fast enough to catch them. I also dont want to be put into that situation. So only the plants and adults are allowed out there.