This is the second time I posted a rather lengthy reply that vanished a moment later. If I hadn't tried to correct a typo, I wouldn't even have noticed it. Is this a common occurrence / bug in this forum?
It gets flagged as suspicious if you edit it too much and the post gets moved into a moderation queue, it'll show up when a mod gets around to looking in there.
It happened to me with 5 consecutive posts yesterday even though I wasn't editing them - I just took it as the forums telling me to stop being lazy and go outside.
Happened to me a few days ago, too. I was replying to someone, than realized a typo, wanted to edit... and everything was gone. Second try, same outcome even without editing again, so I stopped trying and went on.
It's possible your comments got merged. Go into your profile and find your started discussions or comments and check if it moved. Usually if it gets deleted the admin sends you a dm.