Actually, when I think about it, I think it is a perfect thing for one to say under these particular circumstances, if one was expecting his child to be at home where she should be. Can you imagine coming home from a hard night's work and being ready to relax for a while to unwind before going to bed, and being greeted with your girlfriend saying that your child is gone? If it were me, I'm sure I would freak and who knows what I would say. He knew that his daughter was afraid of the dark and would never leave the home in the middle of the night, so the only option is that somebody took her. And his girlfriend supposedly slept right through it! So, his statement sure fits the situation. I'm kinda surprised he didn't say something worse.
I don't cuss, but in this situation, I'm sure that I would be spouting off every bad word I'd ever heard, whether I knew what it meant or not!