My iPod has now come back to life, but it was all very strange. I tried all of those things including a reset without it helping. Finally I called Apple phone support.
One of the things I had tried was to plug it back into my computer, and it did nothing; it did not even recognize that anything had been plugged into it at all, not even an "unknown device" message. I had tried everything the Apple tech suggested in nearly an hour on the phone with him (including plugging it in and trying to get iTunes to recognize it, and trying a reset a couple more times) to no avail and he was preparing to send me a new one under warranty when I said, "I'm going to try one last thing again," (that I had tried before several times already) and I plugged it back into my computer despite Einstein's admonition about the definition of insanity -- trying the same thing over and over again, expecting a different result THIS time.
But THIS time I DID get an unknown device message, with the notation that the device on this port had reported an error condition. It was stil not showing anything in my drive listing, although it showed up as an "unknown device" in my Device Manager, with all properties, drivers, etc. unknown. Because this was somehow different from the way it had worked just moments earlier, I again tried a reset, and this time it worked. The iPod came back to life and everything was completely intact, including having it come up playing the last song I had been playing the day before.
I plugged it back into my computer and it behaved normally in every respect. It sync'ed in iTunes, showed up as a "removable storage" drive in "My Computer," and appeared correctly in my device manager.
When inanimate objects miraculously heal I am always a bit suspicious, so the tech and I agreed to leave the service ticket open and that it would be replaced if it happened again.
Note that I had not left it charging for a long period (about four hours via a USB2 port on my computer) prior to its little crash, and I had used it quite recently (just the day before).
All's well that ends well, so I guess I'll chalk this up to one of life's little mysteries.
