I feel like a horrible mom

I was reading someone real quick while my lo was playing. We always keep the basement door closed, but this time it was cracked a little bit and she opened it and fell down the stairs to the landing. I’m still shaken up about it, but she’s fine now and as happy as can be. She has this to show for it. This is 5 minutes after the fall happened. Has this ever happened to anyone else? Ugh I feel so horrible, but I can tell you I will always double check that the door is closed. 😭