Good News/Bad News:
The screws arrived just before Christmas! Yay! Thanks, @bateske!!
I can't seem to get my Arduboy to work at all, though I waited until I had purchased some thread lock, and then screwed the unit back together. It all looks fine, but absolutely the only thing that happens now is that I can get the LED closest to the USB connector to come up by plugging it in and having the switch over to the right. It doesn't appear to do anything else. Doesn't hold a charge, as far as I can tell, which is to say that I've left it plugged in overnight, both with the switch to the left and to the right (yup, two nights), but if it's not plugged in, there are no lights, no nuthin'. If I plug it into the computer, it does not show up as a USB device in Device Manager at all.
It's dead, Jim.
Even though it was working fine prior to the last screw falling out, and it sitting gathering dust in my drawer for months awaiting screws.
I am so sad. Since I've been on hold, the Arduboy Manager project came to life, and I was really looking forward to using it.
Guess I will await the 2nd generation Arduboy. Sigh...