This occurred to me a while back and it's probably pretty unlikely but I'll throw it out there anyway. I wonder if they have compared the toddler's DNA to any of the potential suspects. I guess I was thinking about (and God forbid, I hope this isn't true) the possibility of one or more of the victims being held for awhile. That would explain perhaps how a child and its mother could disappear and no-one report them (if no-one knew of the child's existence to begin with.) I won't elaborate because it's too hideous to even think about, and I hope that is in fact way off base, but I'm putting it out there because it's not impossible.