No horror stories here either, and I've been an obsessive - and intensive - bum-stuffer for at least two decades.
In the beginning yes, I used to worry about items getting lost in there and travelling up my intestine. But note that there are two important reasons why - in my view, and in most cases - this won't happen.
One --- The peristaltic muscles tend to push things towards the anus, not away from it. It's their function.
Two --- Eventually, anything that *might* try to go too far along the intestine is going to meet something going the other way, and will lose the battle!
Note that I said 'in most cases'. There are things that I would never, never introduce to my anus. Anything with sharp edges or corners, frinstance. Or anything liable to splinter or break. Or anything with a grossly irregular shape. Or anything that might absorb the intestine's natural lubricants and adhere to the internal walls [stories in which feminisewd men insert tampons always worry me!].
And think, for example, about those beautiful, sleek, grass seed-heads that will only go one way when you try to hold them between finger and thumb!