Could/should I have said/done more?

While visiting our DD we took our 3 year old DGD to a local playbarn as the weather was cold. It was a school day so not overcrowded and all under fives. I keep DGD under my watchful eye at all times and venture in as much as I can so I can join in. On entering a sort of padded football pitch to have a kick around, suddenly there was crying nearby. I saw a child 2-3 curled up in a corner sobbing. I said come on let's find Mummy. Couldn't see anyone looking over. He continued to cry and, at one point, I thought he was going to make himself sick. Another Gran appeared and we both tried to console him while looking out for an adult. He then said Daddy so I said come on then let,s find Daddy. Then a woman appeared who said she was looking after him, I said he's been crying for about 10 minutes.she just walked him away. Later I saw her sitting on a sofa chatting to another woman with her back to a table with 4 children eating their lunches (sandwiches) on their own. I was appalled that she was probably being paid to look after these children and she certainly wasn't. My heart breaks thinking of this little chap enduring this "care" and, of course, he can't tell anyone how miserable he is or why. Should I have done more and, in any case, what?