My question is where the check did you find bears? Wife is from Knoxville so we get to the Smokes at least every year, albiet winter. But when did you go? We are planning to increase our exposure to fall, for colors.
I have had a similar problem with my 300 and my 70-200, where the camera locks up, the viewfinder reports f0 (zero). After about 10 secs of fiddling the camera comes to life again. But at an outdoor event this past weekend, I had trouble in broad daylight, where the lens would not focus, and if I twisted the lens barrel it would work again.