We have ferrets so we know what the poo can smell like (trust me, I just cleaned their cage.) Ours are not litterbox trained, not even in their own cage. (We are in the process of training.) And so we make sure that all out of cage play is supervised (they let theirs run around at night in the room unsupervised while they sleep), and if there are any signs of impending poopage (backing up into a corner) we scoop them up and put them in the litterbox/cage. If we don't catch them in time, we clean up the poop. Simple, no?