It went something like this:

Middle: "Can I come down now?" He asks from upstairs.
Me: "Yes, you may come down now."
Middle: "Ok. Mom, I pooped on the stairs."
Me: "You what?"
Middle: "I pooped on the stairs."
This is what I saw when I looked up the stairs:
Little wads of toilet paper. Hmmm...I question the pooper further.
Me: "Middle, where did you poop?"
Middle: "In my pants."
Me: "Yes, but WHERE did you poop?"
Middle: "In my bum."
Me: "How did the poop get on the stairs? Did you poop in your pants and it fell out of your pant leg?" [side bar, he had been sent to time out and in order to get him to go I must threaten removal of Cars decorated clothing items. I removed his pants, then he complied but not before he took off his diaper.]
Middle: "No, I kicked it."
Me: "You kicked it? Where did you kick it from?"
Middle: "From my room."
Me: "So you pooped in your room?"
Middle: "Yes."
While cleaning up, I found this:
Toilet paper on the floor of his room. Hmmmm...I had placed two rolls of toilet paper on the steps, to bring up the next time I went up, at least he knew where to find it!
Edited to add - while I was writing this post - they put this together: I was VERY impressed with this feat!