Here are 2 more pictures. I suppose I'm getting a bit obsessed - sorry if I am wasting your time.
I did eat some fancy mushrooms which it might be, but I cannot remember eating such a long thing: (cleaned with water)
Some other things I put in a 96% alcohol solution: (guess I should wait some days?)
My stool smells like farm animal faeces. Shall I put something in the 96% alcohol solution, to test something for you? Will, for example, the 'white rice' looking piece on the right side of the second picture dissolve?