I was talking to a friend about another friend's DS spreading his poo in his bed and bedroom. How he'd put one "log" by the door so when they opened it, it smeared across the floor! He is only 3 years old. I was really telling it as a funny story but my friend got very serious and said that it's not normal. She works with children so probably knows about these things. She said it's a sign of abuse 
The other family doesn't seem abusive and I know them well. I'm not sure it is serious. Aibu to think it's nothing to worry about?