Being aware at what's going on around you isn't paranoid. It's smart. But, I wouldn't jump to conclusions. Keep in mind that teens have been sneaking out of the house for generations. I'll use the movie "American Grafitti" as evidence.
My best friend and I "borrowed" her dad's Karmin Ghia (is that spelled right?) when we were 16. We pushed it down the driveway before starting it up. We were out all night and would've gotten away with it - 'cept we couldn't push it back UP the driveway