depends on the state but not at fault accidents in many states raise your rates. esp with something like this where even though it's nothing that he intentionally did the ins co could easily say that he was following too closely to have the proper time to avoid the ladder. basically the way to look at it is any time the ins co has to spend money or do work your rate is going up. sucks but for the most part it's true.
My rate didn't go up when someone hit my parked car and didn't leave a note. If your insurance company is being an ass to you, you can always find another one.