As I understand it, if someone reports an inappropriate post, the editor will take a look to see if it should be removed.
Because the editor can't be on duty 24 hours a day, there's also an automatic facility which deletes a post if a sufficient number of complaints are received. (From reading other posts here, I believe that it takes 3 reports for that to happen). When the editor comes back on duty, a decision is then taken as to whether the post should be re-instated or not.
The list of possible reasons for people to object to a reply is as follows:
Duplicate answer
Irrelevant Answer/Chat
Profane
Sexually explicit
Abusive
Advertising/Other
Imposter
I rarely report posts but, when I've done so, the most common reason have been 'chat' (I would normally only use that for questions, rather than for answers), 'abusive' and very occasionally 'advertising'. [Before someone accuses me of being one of those people who spends all of their time censoring other people's posts, I should point out that I've posted nearly 4000 answers but reported fewer than 20 posts].
If you look through those reasons, you might be able to work out why your post disappeared.
Chris