Awkward moment

I was doing a Mommy assisted event at my son's school and I ended up with one of those moments where you wish you could have done better. Here is what happened

Other Mom: Hi, I am X
Me: Hi, I'm __. Nice to meet you blah, blah, blah
Other Mom: Which child is yours?
Me: Oh, my child BB other there in the green. Which child is yours?
Other Mom: Oh, my daughter is little X.
Me: I don't know the girls. Which one is she?
Other Mom: Oh, there she is, over there in the red hat.
Me: Oh.

Now, the child she pointed to is of another race. Her father might be of that race or she might be adopted. I had one of those moments where I drew a blank. Maybe in my mind, I was ready to comment something like "She looks like you" or something like that. Instead I drew a blank and felt like a jerk. Sigh.

What should I have said? I suck at small talk.