As strange as it sounds, I believe the parents.
I do not however believe that this "mistake" or "oversight" excuses them from being punished to the highest degree.
The reason I believe them is from a personal family friend of mine. His family went to church with our family. It ran around 600 people during these years.
At least 3 times over the course of about 5 years, church would let out at around noon on Sunday... people would stand around talking, saying their goodbyes, etc. 'til around 12:30-12:45... then we'd all load up to go to lunch somewhere... arrive at lunch anywhere from 1 PM to 1:30 PM... wait for the table for our usually large group... be seated around 1:45 to 2:00 PM.. then they'd notice that his youngest brother, or sister was not in their seat...
They'd do a quick scan.. the parents would meet eyes... "I thought you got him!" "What?" "Oh my goodness!!" The dad scurries off down the road... half an hour later their back at the restaurant embarrassed, but with "missing child" in tow... the kid had been asleep on a pew (church bench seat)...
I witnessed it at least three times in 5 years, involving 2 different siblings of my best friend... at times when the family was either 5 or 6 members...
Of course it helped that the dad was a bit of a goofball, and that the mom was scatter brained.
Yep. The gene pool will survive... they are all having kids of their own now.
But I can see them (my friend's parents) in my minds eye when I read this story... I'm even more relieved now days that they never went to WDW... I used to be mad that they wouldn't go with us in the '80's...
----Just remember, the second you think you are above being an idiot in any one situation... you might be the one who does it.
---As for my family, our rule is "hand-in-hand" with either Mom and/or Dad at all times not in a ride seat... and no one goes anywhere unless our hand is in yours... the only exception ever was while my daughter was buckled in her 3 point seatbelt inside the stroller...
But, I am thankful this has never happened to me.. and that I was actually a witness to this type of hair-brained activity when I was kid... I knew long before I was grown that I would always pay attention to my child's whereabouts.
--To conclude: I believe the parents. I believe they should be severely punished. But sadly, I believe they'll get a slap on the wrist and get the kids back.
-And... to those suggesting the parents be locked in a car out in the heat... my Lord, please don't wish evil on other people unless you've already found out for a certainty by way of personally interviewing them that they did this type of thing on purpose. I'm sure they felt bad enough, and continue to feel badly - and will accept the punishment they receive, how ever light it ends up being.
But seriously, you don't want to wish this on your worst enemies...