I think it’s far more plausible that Spock simply didn’t scan for life signs, as his mission was to install the rockets and had nothing to do with rescuing any survivors in the first place, he stumbled upon Chapel by accident. It’s also logical to assume that there would not be any other survivors left in the same space as Chapel as from Spock’s perspective, she would have brought such along or at least have informed him of them. Therefore, we can conclude that there wasn’t any misconduct from either of the two.