So it looks like one of our 2 cats or 2 dogs has left us a present.
Well, I cleaned it up as best I could. I sprayed the leather with
Lysol cleaner. Then leather cleaner. Then leather polish. If I put my
nose up to it, it still smells. If I sit at the other end of the
couch, I swear I can smell it. Perhaps the smell is just "in the air"
(or in my NOSE!), and it will dissipate and go away on its own.

Make sure there are no other mouse "parts" still in/under the couch. My cats
like to spread their victims around.