Last week DestructoBoy was hit quite hard by a nasty headcold. Lots of sneezing and drippy nose activity. The only thing for it was to be all snuggled up under blankets on the couch with a steady supply of good books, strong tissues and living hot water bottle.
Even when DB felt sufficently well to get off the couch the hottie stayed in place, keeping very still among the folds of the 'chinchilla' and trusting in the power of camouflage.
This is when he went into 'stealth mode' and hid under the blanket.
Sadly I am not so sure the black dog has quite grapsed the principles of detection evasion. I feel sure you have to obscure more than just your head.