If it was water shorting live to earth and/or neutral and tripping a 40 amp fuse there would be clear signs of corrosion and other damage at the place where the short occured.
It isn't impossible that there is a junction box somewhere that was soaked by the water or the back of the cooker box.
It isn't impossible that there is a junction box somewhere that was soaked by the water or the back of the cooker box.