FOUND HER! That was it, she was behind the refrigerator which was very nearby. I got my flashlight and took another look under -- and saw nothing. But this time I thought I'd pull it out and see if there was another crack or hole she could have gone through back there. And she was hiding right smack behind it.
I was tripped up on two ill-conceived ideas:
1. I thought I was seeing all the way under the fridge from the front but I wasn't.
2. I couldn't imagine how in 5 days she wouldn't have explored further and tripped one of my cornmeal traps. DVirginiana as right and she'd hardly gone anywhere.
Hopefully this will help someone else one day.