I don’t know about android, but on Windows with MS Edge I occasionally lose posts.
STW have removed the issue where you used to be able to post to no forum and the post would vanish. In this instance you used to be able to hit the <Back> icon and your post would be intact.
Occasionally I trigger some sort of security bot that lurks within the forum and takes exception at the use of certain word; you end up on an almost black page with Forbidden written in tiny text at the top left.. Now if I go back my post box (but oddly not the title) is blank and the post’s gone.
I don’t know if the vanishing post issues exists on android (although I suspect it’s a site issue) but the next time you lose a post on android you could try swiping back just to see if it’s still there (I suspect it won’t be though).