When it comes to Microsoft Natural keyboard this is unfortunately quite a common experience, i just lost a second keyboard to a small water spill. Interestingly enough almost exactly the same keys stopped working.
The keyboard is a membrane keyboard. There are three sheets of plastic, with middle one having small circle cutout, through which bottom and top layer may contact when the key is pressed. When you spill water on the keyboard around middle section it will actually follow the incline, and go down on top of the membrane without entering it. Then it will pool in the place pointed out on the picture where incline ends.
Then water will enter the membrane from the side. On the membrane you have conducting lines, that are sort of printed on, sadly seems like water basically dissolves those. On the second picture you can see the spot where I took of first two leyers of membrane to show the bottom one. The gray lines, actually are no longer conducting (I checked with a multi-meter)
So the only way to fix it would be actually to use some wire glue or conductive silver and fix up the connection manually. I will try that next but it will require some serious precision work.
I suppose the best course of action if you do spill water on your keyboard would be to immediately unplug it, flip it upside down, to limit water contact with membrane, and then stuck it in a plastic bag with rice / silica gel hoping that the permanent damage has not occurred yet.
