Yeah, I learned that same hard lesson last year at about this same exact time of year. The bears love cool spring nights because after they knock over the hives the bees get so cold that when the bear comes back for round two of honey buffet, most of the bees are too cold to sting.
Structure fences just don't work with bears.
This might sound mean, but if you suspect that bear will be back tonight, you can aquaint him with the power of your fence. Pop a hole through a freshly drained metal anchovie can, and then wrap the hot wire into the can and smear some bacon grease and peanut butter in the can. That bear will be sure not to visit your fence again.
Granted. You don't need to do this to ensure that a fence works...I guess it just feels nice to give the bear a little payback without the use of a gun.