Yes. People would go into our maintenance closet where mops and buckets were stored and had a big sink.
They would sit in the sink and do it, even though the restrooms were more available and convenient. I've also seen people leave a trail as they walked through the store. Also found a guy who died in the process, though at least he was sitting in the toilet in the Men's room.
I had an elderly customer do it on the floor mat in front of the meat case, it was terrible, we called a couple of baggers to take it out behind the store and one threw up, poor guy.
I have actually seen something similar to what Jim Henry said. The guy took a dump in the bathroom sink then for some reason smeered it all over the mirrors and walls. I was the first person to walk in there after it happened. The smell was so bad I almost puked. He also left a trail going from the bathroom to the front door. A couple weeks later I was hanging out with the security guy and we talked bout that and he showed me the video f the guy leaving the bathroom. The guy was intentionally dragging his foot all the way down the isle to smear his **** on the floor. This was not someone elderly or mentally confused. I found the experience very eye opening to how disgusting and repulsive some people can be. Before that I could never imagine someone doing that on purpose.
The first job I had after I left the business, I had 2 techs who were brothers who regularly did this to the mens room (smear it all over). I'm not a psychiatrist but if I was I bet I could tell you there is a specific name for this condition. Of course once we were able to prove it, they were fired.