Just to also add a few points from a wiring manufacturers persecutive (if I was one of course
The CB (or fuse) is their to protect the building wiring from Overload, Short-Circuit, and Ground-Fault. They would not have detected this condition as stated by the OP, as well noted by our fine members. The misconception of an OCPD (fuse or CB) is that it is to protect the equipment to which the building wiring is connected too, other than electrical equipment to which "conductors" fall into such a category. What is important is that we get a chance to see yet another REAL example of how a GFCI (which not perfect and 100% affective in all cases) could have saved this child's life.
A standard Circuit Breaker is simply a unsophisticated device that looks for either a magnetic or/and thermal component to it's internal operation, for the aforementioned conditions to which I already expressed. A GFCI equipped OCPD or Receptacle type device would raise the level of protection on this circuit. However, lets keep in mind that GFCI devices (CB or Outlet) can be fooled if a direct connection is made from the grounded to the ungrounded conductor in such a way that the "object" is assumed by the circuit as simply a load. So while GFCI devices do save lives and should ALWAYS be used where directed by the NEC (and other areas if applicable to your level of concern=over and above the minimum code standards) lets never forget they are not perfect...but it's the best we have to aid in preventing such incidents as the OP presented.
Ok...i'm over that now..on to other topics