'If she died earlier in the day and her corpse was disposed of, then that is the prime cause.'
Do you give credence to that theory ?
P.S. As they were left alone, assuming nothing happened before that evening, then the prime cause of her disappearance is the fact the parents weren't there. What happened afterwards is probably something we will never know.
Just seen your edit.
You do not understand what a Prime Cause is. A prime cause is an event that of itself ensured that the event happened. Events that merely make it possible for an event to happen are subsidiary causes.
For example, if (to lower the temperature of debate) there was a theft a holiday apartment resulting in the loss of valuables, the causative chain would be:
Events of the people from birth to-
Deciding to go on holiday
Deciding to be at that place on holiday
Going there
Deciding to go out to dinner that night
Failing to put the valuables in the safe in the room
Leaving the lights out
Not locking the door
(up to this point all are subsidiary causes)
Thief enters the room and steals the valuables.
(this is the prime cause)
All the subsidiary causes could happen (may have happened on previous nights) without the theft occurring. The primary cause is that event that is necessary for the theft to occur.
The only case in which their abandonment was a prime cause would be woke and wandered if we accept that a three year old is not the only cause of their behaviour.
The only possible Prime causes of Madeleine's disappearance are that of the example above, an unknown abductor, or harm from a family member followed by a cover up.
Leaving the children alone was an error but can never be the Prime cause of abduction or cover up.