I accidentally asked out a middle schooler

Today I (M27) was grocery shopping, and I see this woman walking by me, she looked about 5'4, so she was on the shorter side. She was wearing a shorter skirt and like 2 inch heels, so I didn't think she was a minor.

I get her attention while she's walking near me, and just act casual and say, "Hey, I thought you were really pretty, is there any chance your single?" She pauses for about 5 seconds and then says then says, "I'm 13." I say okay and back off and start walking and that was it.

I can't fucking believe I just asked out an 8th grader. She looked mature and not like what your average kid is like, so I didn't think I was asking out a child, and I only saw her from the side. That's the last time I ask out a random person at a grocery store.