This morning I was replying to a message about formatting a hard drive, and when I hit "Submit" it took me a log-in window. Being a guest, I can't do that.
So I went back to the Forum, and the thread about formatting had disappeared.
Maybe the guy who post it decides to delete his post while you were writing your reply...
Sorry about this
I posted a question but then realised the answer for myself so deleted the post so as not to waste someones time trying to help me