Yeah, it is hard to understand how anyone couldn't sense a bear sneaking up behind them until it decided to smack 'em across the back of the head. I wonder if he was hard of hearing and/or went into the woods smelling like a flower. Something must have attracted the bear(s) in the first place and then provoked the attack. Just one of those annoying little details we'll never know.
I think the main thing to is keep your eyes and ears open. Make a little noise once in a while. Avoid using sented soaps for washing yourself and clothes. Try not to smell like something good to eat. If possible, protecting your back sounds like a really good idea. I'll have to remember that one.