One of only six children at the America's Kids Day Care Center on the second floor of the federal building to survive the explosion, the blast tossed P.J., then 20 months old, onto the sidewalk below. But although the toddler was alive, his 33-pound body was battered almost beyond recognition. For the first 30 days after the blast, P.J. remained in the intensive care unit at Children's Hospital, while doctors battled the fevers that raged through his body.