Do feel for the engineer who was at fault though... but how do you not notice that a test carriage hasn't returned back to the station? If the ride sensors are flashing and saying there is another carriage on the track, then surely you would check that out before overriding the safety feature that stopped the full carriage? That is a severe mistake to make - did they actually choose to just ignore the ride safety sensors? It's just all so bizarre!
My theory is that this was a 'boy that cried wolf' scenario.
Throughout the day the ride had been experiencing multiple stoppages all the time when there had been nothing wrong with it. From guest reports on the day these stoppages were short so I suspect it was due to over sensitive sensors shutting down the ride for no reason. Each time it happened it would of been investigated only to find out 'hey there is nothing wrong here'. In a cruel twist of fate the one time the sensors stopped the ride for the right reasons the engineer probably thought 'im getting fed up of this, there is nothing wrong with it' and restarted without checking.
I must point out this is only my theory and I have no evidence to back this up. But like you said I cant for the life of me think of any other reason why they wouldn't of bothered to check?