Me, too.
Don't know why, but I wrote one, pressed preview and it disappeared. So, before I tired again, I drafted in Word and copied it to be prepared to have to do it several times, and it worked right on the first try. I don't know what the trouble is, but it's been reported to me by several people.
Here's my offer: if it happens to you, feel free to send your (signed) comment to me and I'll post it as a comment or a new post, whichever you indicate to me.
Hope it's just a momentary glitch in Blogger...
Best wishes, Sara