Occasionally I'll find poo on the floor, and it could be far from the litterbox. Sometimes any of my three Himalayans might have a poo stuck to their butt fur and they'll eventually shake it off well after leaving the litterbox, or I'll grab a tissue and remove it myself. I don't really worry about it.
A few weeks ago my Silky was using the box - and eventually she came tearing downstairs with a big poo stuck to her shoulder. I'd give anything to know how she managed to do
that! Took me a minute to catch her in order to remove it.