I can't begin to tell you how sorry I am about your fire. After people and pets, I would consider the most devastating loss to be the loss of my books.
You're absolutely right to point out that the Spodoptera ornithogalli larva and the Noctua pronuba larva can look incredibly similar. The way that I tell them apart is to look for a large black spot on the side of A1 above the spiracle. This spot is often (though not always) seen on the Yellow-striped Armyworm, but not on the Large Yellow Underwing.
I'll paraphrase about the Yellow-striped Armyworm from Wagner's caterpillar book: Abdominal segments frequently with set of four, thin, white stripes beneath subdorsal stripe...Often with a black spot on A1 above spiracle...Many have rusty line beneath each spiracle which may join to form thin subspiracular stripe.
I've added a few photos which show the details of the anatomy I used to identify these fellows.
I didn't rear these to adulthood, but I'm so glad that you got to see your Noctua pronuba through their development. I wish you the best of luck in replacing your books - what a terrible loss!

the caterpillar shotguneddie linked to is also a yellow-striped armyworm, correct?

Yes, I agree. In fact, it looks as if it has just been re-identified and moved to the Yellow-striped Armyworm page. :)