I saw a hijabis hair accidentally

I’m a man (16) and at work I was helping a hijabi customer and while I was inputting information on our computers and I looked up briefly and saw her adjust her hijab and her hair was out for a second or two. She didnt seem to notice as she wasn’t looking at me but instead at her friend. I feel bad. What do I do? I’ve heard that men aren’t allowed to see a Muslim woman’s hair. I myself am also not Muslim and am more of a non-religious Hindu since I was born into the religion.