BTW, DS had less interest in that cereal, it tasted bland and boring AND it didn't look or smell as nice as his usual one.

I just keep thinking what if that was a 4m old baby, no formula and had a reaction. When the mum went to the hospital she may not realise her baby had been eating formula.

I'm not anti-formula and DS has had formula, but when I gave it I always knew in advance I was buying formula, making the bottle, giving formula. To sneak it in like that is pretty poor showing.