Occasionally someone complains that they wrote a long post and then it did not post or just disappeared. I have had similar things happen to me and I suspect the issue is a sort of time limit imposed by forum software. If you start a post, leave and then come back later to finish it, you may have been “timed out.” I’d suggest, when you are doing a long post or plan on finishing it later, that you either post what you have written and just add on later or do a copy/paste of your draft so that you have it saved in other software.