Six Pack or Keg?

Ever notice how nice and flat your stomach looks when your laying down. I noticed that mine was looking awesome the other day in Pilate's as she had us lay down and stretch out. Wow! Its so flat, is that my stomach...I check again...yep, its mine. Then I sit up..Ugh...yep its mine. Where does it go when you lay down? In your back? Then I'd look like I was laying on a hill or I'd look like a camel. Is it just on this inside of my body? Why can't it stay there when I'm sitting or standing. Is it possible to still have my active life and somehow be horizontal so that I have my flat stomach? Can I walk around in a back bend all day?