Gosh, that is low, and a big drop in 3 hours. If you didn't feel anything, did you test again to check it wasn't a dodgy strip giving a rogue low reading?
It looks like you went down so fast that I can imagine what you felt wasn't in sync with your bg. What happened to make you drop like that? If you know what caused the fast drop and it doesn't happen regularly, and if you usually feel your hypo's a bit earlier I would count this as a one off unless it happens again.