Correct -- this is what people don't understand about fingerprints. They simply believe that it must have been wiped, when in reality, fingerprints aren't always left of certain surfaces, depending on skin type and the amount of grease. Not only that, but prints can evaporate as well. I'm not saying the flashlight wasn't used in the murder at all -- I don't know -- I'm just stating a fact: simply because no prints were found on an object, doesn't definitively prove said object was wiped down. It reminds me of the Kurt Cobain case. There were no prints found on the shotgun, so people automatically assume it was a murder. That isn't the case, at least necessarily.
What we can say, definitively, is that there were no prints on the flashlight nor the batteries.