The location of the pain is about, from an upright sitting position, five inches down from the right nipple and one inch south. Right at the bottom line of the lowest rib.
It almost only happens during exertion, and almost only happens during very tight calorie deficits and when eating unbalanced meals beforehand, like brownies and protein drinks with fat free milk.
While running I start to feel a mounting sharp pain in that area that becomes larger with continued exertion, similar to precordial catch pain if you've ever had that but in a different location. If I let it go on for too long, breathing will make it hurt worse too. If I stop exercising, the pain doesn't get much worse, and then dissipates slowly after 15-30 minutes.
As for people being able to feel things moving around in that area, it's not unheard of. I only felt the movement those two times, last night and again after eating my meal with healthy fats earlier. It was pinpoint in the exact location that the pain has been in, which is very far removed from where I feel gas, stomach pains, heartburn, or heart palpitations.
Considering the location and type of pain, the amount of weight lost, and my diet leading up to it (a lot of red meat and fat, big calorie deficit, and the calcium supplement) it seems like the best explanation. I realize that I'm inferring dynamics from kinetic data, but I can't exactly go to the doctor and ask them, so it's the best I've got. It seems like some people describe gallbladder pain differently, with differences between males and females, but a subset of people like me seem to only describe upper right quadrant pain.