I’m assuming that most adults would assume that a five year old child is capable of going to the bathroom without supervision (that’s Kindergarten age) and if the child said nothing to them about being in any pain, how would they automatically know?
I would question my child rather carefully as well as my parents before jumping to any conclusions.
Whatever I found out from those (non-accusatory) inquiries would determine my course of action.
I remember being a little surprised that long after he was completely toilet trained, my nephew routinely called my sister in to wipe his butt. He was not the most ambitious of children, to put it mildly. Being the firstborn son in an Italian family had accustomed him early in life to being rather coddled.
It was her developing painful bursitis in her shoulder from hauling him across the courtyard of their apt. complex to do the laundry which finally propelled her to insist that he walk (at 3 yrs. old finally) instead of being carried.
Likewise, a few months before his first day of Kindergarten, she put her foot down and told him that was now his responsibility to wipe his own butt since no one at school would be volunteering :) There is a limit, she figured, and that had been reached :)