The cause on the vanishing act is that you have exceeded the allowable characters (not words) for each post. Your construction is actually still there. Simply go back and click on "Post an Answer" again and voila, it will reappear intact. At that point, simply use naomi24's solution or just scroll your reply down about half way, highlight the entire LAST half of your answer and the select "cut" from the Edit bar at the top. Submit the first half, re-select Post an Aswer and select "Paste" for the second half and then submit in two parts.
Cumbersome, I know from experience... but that's all we have for now. I've asked for a warning of some sort when one tries to submit too long of an answer (which used to exist in the previous itieration), but to of no avail... yet. Hope springs eternal, no?