Is this the same kid in the cloth diapers that leak all the time and the parents are not doing anything about it?
Something I can tell you with 100% accuracy is that when a problem is only made to be YOUR problem and never affects the parents then YOU will pay the price for it every time. Once you turn that problem back on the parents suddenly it gets fixed. So, in this case, CALL for pick-up and make the parents leave work to come get their leaky, poopy kid and go home to bathe him.
You see, it's only an inconvenience to YOU so they don't see a problem with it. Once it becomes an inconvenience to THEM and they are in trouble for having to leave work to come get their kid a few times only THEN will they fix the problem.
This is THEIR child - not yours. Make them deal with their own problems. Don't adopt problems for them or fix them.