pee pee on the patio

"F'llow me, Mom. F'llow me!"
"What is it, sweetie?" I said to my daughter, who is 3 years and two days old.
She waved her little arm and waddled to the sliding glass door. "I went pee pee right here," she said, pointing outside.
"Yes, you did." Indeed, a puddle on the patio marked the spot.
"Now, I don't have to go pee pee in the potty."
"OK."
How could I argue?