I still don't know whether all of my posts were erased by a problem with Blogger's software or servers or what. Sigh.
Past entries are being re-entered, and this time I'm saving the HTML for each one in offline documents so that I can hopefully get them right back up if this happens again, but I'm also looking into other hosting options. (Extra weird? Today, all of a sudden, I’m finally able to paste text into the regular Compose window.)
The Blogger Help Group has a page titled My Blog Is Gone whose first sentence is "We're hearing that cry of dismay a lot recently." Although my blog isn't actually gone, I'm not exactly reassured by reading that, nor by seeing accounts of hijacked blogs in the Help Forums. I wouldn’t presume that this was malevolent, necessarily; since my password is entirely nonsense, however, Blogger needs better security, more failsafes against massive technical glitches, or both.