Being "mentally handicapped" is of just that....Mentally handicapped and not capable of making sound judgements/choices. I think i would opt to blame the parents of this child as they are the ones truly responsible.
However...There are lack of responsible parents even to "normal children", etc,
I am glad Toby is ok and I am sure you were very upset by the situation.
Maybe next time hide Toby in the basket of laundry, LOL!!