Never run across that before, and I have a lot of tablets.
One possibility is that it was a fluke and something else woke up the Nook - any way to test it with device asleep but the case open?
Another possibility is that the Nook and the Samsung were paired at some piont for doing bluetooth file sharing, and the Samsung scanned BT and that managed to wake the Nook?
Dummy me! Should've tested the way you suggested. Have done it twice without the case (removed the case entirely).
Guess that what happened was a fluke; blue tooth is disabled in all 3 of my tablets.