You're lucky your child has avoided such a scary situation. I agree that it is every parent's worst nightmare, and it's every parent's responsibility to keep their children as safe as possible too. We can never be too careful!
It might be a good idea for all of us parents to take some time to ensure our own window panels are properly secured, especially those of us who live in older HDB blocks. Better safe than sorry, as they say! It's also good to remind our kids to stay clear of tall buildings and keep a lookout overhead when walking underneath them, just in case.
Have a lovely day ahead!