That's absolutely mortifying, on the parents part. Why can't parents supervise their children adequately in places that they're well aware will have irreplaceable artefacts? This wasn't a child bumping in to it, he was bloody pulling on it. Child doesn't know better - but parent does!
Don't know what the museum are thinking either not having them behind glass. These things are supposed to be 'look, don't touch'. They've responded in a very nice way, good on them. But honestly, is nothing sacred?