Whew! Found it!
That elusive third bunny emerged from the kitchen just now (you know, the kitchen we searched FOUR times!), sending the dogs into a mad scramble. My beloved DH managed to snag the madly shrieking little furball and get it back outside near its original nest. Dang those things are quick!
Boy, I feel much better knowing it's not trapped inside.
So ... The Bunny Hunters are now officially out of business. LOL!