If you really want to, you usually can run out of the enemies sight (especially with BoS), hide and then return into the fight. And yes, there are a few fights were you're unable to lay traps in advance.
And scrolls are not to be underestimated, if of cource not as usable as they are in the hands of a mage. If they were, the thief would be the strongest character ever, hands-down.
A well-equipped fighter will never ever be able to take down a well-equipped thief. He wouldn't ever had the chance of seeing him, and the traps would slay him outright. The only exception would probably be the Inquisitor. ;o