There were certainly stewards elsewhere in the North Stand who had seen the smoking light well before anything fell from the fitting. There were also club staff on the pitch who had seen it. I'm surprised that an appropriate warning message hadn't reached the seats where the debris fell well...
Hopefully so. But from a health and safety point of view, you have to ask the "What if ...?" question and realise that the answer to that is that a very serious injury might have occurred, given that preventative action wasn't taken in the couple of minutes before hot metal stuff started...