Hi J.,
Isn't that the craziest feeling?! I haven't been (and cannot become) pregnant for over five years, yet I STILL have 'phantom kicks' now and again. I've noticed that my mind only qualifies them as 'kicks' if I'm engrossed in some other thought, so that the part of my mind dealing with the sensation is not the portion I'm using for the task at hand. My theory is that in these cases the mind reverts to stored information (memories) and categorizes the sensation accordingly. Naturally, after childbirth when the abdominal muscles are thinner, stretched out and recuperating ALL digestive processes feel more pronounced. The lack of muscle tone in the abdominal area immediately following birth will likely be the reason you (and I and many others) can actually see the motion in our bellies.
Kinda gross and underwhelming, but after years of talking to friends and family (all medical professionals) that's the conclusion I've reached.
:-)