I agree with hamster-bamster it maybe that a public display of affection embarrasses him. There are many possible explanations for this, as mentioned in other posts. However it is possible that he deleted the post in order to conceal the relationship from other Facebook friends. Concerning that, I would say trust your instincts, if this forms part of a pattern of behaviours which makes you doubt his honesty then you should confront him about those things. But I would echo the advice of other posters; don't rush to a conclusion.