For sure you did the right thing! I would have asked DCM to get her ass over here and clean her son's crap off my walls!!!

Similar situation happened to me yesterday....16m old girl wearing a cute lil dress (she always come dressed in only the cutest, best..... blah blah) anyways, no bloomers or underwear on top of her diaper.
Sure enough she has a diaper full of diarrhea and it comes out the bottom. on the carpet, chairs, and her legs, thighs etc.
i text mom saying going fwd she needs to have 2 layers of clothing under a dress or skirt. explained what happened. no apologies nothing, just said "yeah okay, winters coming anyways so she wont be in dresses for much longer". This is not the first time this has happened with her.
Ticks me off that the parents dont respect us even a little bit to express this with a simple "oh no, thats too bad that happened, sorry about your house!".

For that mom to laugh it off!!? omg SEE YA!!!!