But if you roll no skulls does that count as a miss and the monster doesn't wake up.
Not the way we play. It counts as a bungled attack that wakes him up without hurting him enough to kill him. (It'd be a bit hard to miss a sleeping monster with a great big sword, I reckon. That poor Barbarian would never hear the end of it.)
The EU card says the monster "can't defend if attacked" and also "will wake up if attacked". Therefore, as I read it, he must wake up if you attack but score no skulls. It's the only way for both parts to make sense.
If you had scored any skulls he'd be dead (because he can't defend and everybody in the EU base game has 1 Body point). But if rolling no skulls counted as a miss, he'd never wake up, so the bit about waking up if attacked would never happen. Which would make that part of the card text pointless.
Silly ambiguous badly edited card. *tsk tsk* Play it however you want! (Cool idea about having other monsters wake him up... though they'd probably need at least one Mind Point to do it. Zombies would just wander by oblivious...)