When was the last time that someone besides the parents saw the little girl (time lapse between her being seen in public and the time the parents claim she disappeared)?
Any speculation on what the sedative might have been (if at all)? Are we talking high power stuff that might have left a paper trail in procurement? Or over the counter stuff? I don’t know about the UK but in Portugal I think there is pretty good access to strong meds over the counter. If they obtained drugs through their medical practice wouldn’t there be some record of that in the UK?