Did it lay down flat, or did you feel it slide at the rear?
My 05 went down on a round-about 2 years ago when a truck had dumped sand on the road, I was only doing about 10-15kph at the time as its a tight turn... the front just slid away, mainly plastic damage which sounds similar to what you are describing.
Once the front starts to go like that you have no hope of keeping the bike up because of the weight, and you'll be sliding on your side before you know what is going on.
Different feeling with the rear, it can break traction, slide and jump around a bit and you can still catch it and keep it upright with careful acceleration and braking control, and maybe a bit of help from a foot on the ground.
Sounds to me like you lost the front on the wet and bumpy road.. you're just a passenger then.
It pisses you off, but the only thing you can do is slow down a little more in those situations, try not to lean the bike as much to get around the turn, keep it more upright and steer slowly around the curve.
I wouldn't worry about it 2-up.. you've learned your lesson I think... much like I did!
With Ms Precious
on the back, it never slides!!