I think if you look at your owner's manual it has a diagram showing where the VIN, Engine Number and Key Number are stamped on the frame.
OK, my mistake. I looked at the book and it has VIN, Engine and Color but you can get the key number with the VIN if you call Honda or check with a dealer. They should be able to get it. They are going to need some proof of ownership I would guess before they give you the key number.