I wonder if maybe HEnry wasn't sent out by the Others to infiltrate their camp, and knock their leader and the most intelligent/curious person out of commission. By confusing Locke, the true beleiver in button pushing, and perhaps the only one who might ever figure out what is going on, he forces Locke into wasting his energy trying to figure out wether or not he pushed the button or not, rather than organizing exploration parties and raids... Maybe Locke IS his mission.