Unaware is simply the opposite of "aware." If you are unaware, you have no idea what's going on.
To be unaware is to be totally incognizant (but not incontinent). To be "caught unawares" means you were caught off guard or by surprise. Either way you've got your head in the clouds about something. Now some people might say that ignorance is bliss, but the guy in the crosswalk who was unaware of the bus barreling down on him at full speed might disagree.