I thought Bob, rest his soul, was not even carrying a rifle when he was hit by the buffalo.

I am in the same boat as you. There may be grizzly in the area but I'm carrying a rifle for the game I'm hunting.

When push comes to shove, I trust myself to protect my own butt, however there is a sense of security when there is backup and I would hope a PH would do his all to help me if the case arose. And like Ray said, I would come to the PH's aid as well. I think it is better to think of the PH as a hunting partner rather than a babysitter.