As MTI has pointed out, the only reason this has ever been discussed is that Madeleine's mother suggested it. Despite her later claims there's no evidence that the PJ were informed until it was reported by Ricardo Paiva that Kate spoke about it to him "three months after the disappearance."
Strangely, Kate also made several requests, three months after the disappearance of Madeleine, that the police should take blood, hair and nail tests of Madeleine's twin siblings, because, as she said, she remembered that on the day of Madeleine's disappearance, in spite of all the commotion and noise made by the authorities and other persons who were looking for Madeleine in apartment 5A of the OC, the twins never woke up, having been transported to another apartment, they remained asleep, due to which she now presumes that they were under the effect of some sedative drug that a presumed abductor had administered to the three children in order to be able to abduct Madeleine, a situation which Kate refers to being possible according to what she read in a criminal investigation manual given to her by the British authorities, that would have been the procedure of the abductor in the real case involving abduction, rape and murder of the girl.
https://www.mccannpjfiles.co.uk/PJ/SERVICE_INFORMATION.htmLater still, Kate raises the possibility in her book;
I wandered into the children’s bedroom several times to check on Sean and Amelie. They were both lying on their fronts in a kind of crouch, with their heads turned sideways and their knees tucked under their tummies. In spite of the noise and lights and general pandemonium, they hadn’t stirred. They’d always been sound sleepers, but this seemed unnatural. Scared for them, too, I placed the palms of my hands on their backs to check for chest movement, basically, for some sign of life. [madeleine]
Scared? Checking for signs of life? Blaming the police for taking no action? A serious accusation. Only on examination of the evidence does it become clear that the police weren't informed. The obvious question then is why not? Why didn't this mother insist? Why didn't she call an ambulance herself? There is no credible answer imo.