Bad Parenting Moment

I took my son to school and came home and I was on the computer and I saw it was only ten am. I must have gotten over focused because when I saw the time again, it was 11:29 and school had gotten out nine minutes ago. So i got off and told my Dad I had to pick my kid up and I left my baby with him. it’s only a five minute drive to get there so I got there in no time and I saw my son walking with his teacher. I felt a little embarrassed because i didn’t pick him up. I parked and got out and was apologizing saying I lost track of time and she said “it happens.” Then she said she had just called and was that my dad or dad in law she was talking to and I said it was my dad and asked what did he say and she said he said I was on my way. I am sure other parents have done it but only once in a while is fine but doing it often may raise concerns and get social services called. I just hope this was a one time thing and I won’t keep getting hyper focused I forget about the time and then forget to pick up my son. What was I doing for a half hour after seeing the time? I remember I was working on my story and my daughter was with me. Was I busy with her too? It feels like I stepped out of reality because I can’t remember. My son even thought I wouldn’t come. He wasn’t crying or anything when I got there. But I saw he was very happy to see me because he got a big smile on his face and shouted “Mommy” and hugged me.