The Case of the Disappearing Water

A funny thing happened to me today.  

When I came home from work, I decided to make some Macaroni and Cheese for dinner.  The first thing I did was put a pot of water on the stove to boil.  

 While waiting for the water to boil, I went to the living room and began reading.  About five chapters later, I remembered that I was indeed cooking dinner; but, when I went back into the kitchen, my pot was completely empty!  EMPTY!  No water!

 

I should have seen boiling water, like this:

Or boiling water, like this:

But my pot was completely empty.  Not a lot of boiling water.  Not a little bit of boiling water.  GONE! Did my doggies drink my water?  Did leprechauns steal my water?  Any ideas?