When I read about butt plugs, they always mention the flair at the bottom; intended to prevent the body from "sucking" the plug deeper into the bowels.
Out of all the plugs I had made, I had never experienced that problem and had never really tried to prevent it.
I avoided putting much of a flair on my plugs, because the flair is what always made it uncomfortable to sit down.
Then it happened. It actually made a slight sucking sound, but I was relieved to find I could easily reach up inside and pull it back down. That's when I decided to embed one end of a silicone impregnated retrieval chord. I thought it might be nice to have it dangle down reassuringly between my legs.
But since I seldom go out in public anymore, I switched from plugs to "sticks". Long wood dowels covered with silicone, that I use for exploring the depths of my ass. I guess that would be some form of easy-chair spelunking. :-) The sticks are of various diameters and feel wonderful. Be patient and you'll be surprised how far they will go up inside you.
I've said all this just to tell you that after I managed to get a 10" stick all the way in - I tried an experiment. Still wondering about how to deal with something being "lost" up inside, I used the tip of my finger to push the stick as far inside me as I could.
I waited a couple of hours, to see which way my intestines would move it. Then stuck my finger back inside me, halfway expecting the tip of my finger to reach it. But no; nowhere near.
After giving it some thought, I threw myself a party and started eating everything in the house until I was stuffed. A few hours later, I blew it out like I was "throwing a rod".
That's not conclusive, but it is interesting.