Regression

It seems we may be having some potty training regression for some unknown reason. Yesterday we were at the Children's Garden and he was grabbing himself. I must have asked him 10 times if he needed to go potty. He denied it. But when we hit the sandbox area, he suddenly just stood up and peed everywhere. He didn't even mind that he sat in his wet clothes for another hour. He hadn't had an accident in forever so I stopped carrying around extra clothes. Then again today we came home from school and he peed all over our living room floor. I made him clean it up (which he hates) and he was slightly more upset about it but not by much. I hope this doesn't become a pattern, he was doing so well....