I feel like a terrible parent right now

My 5 yr old daughter just started kindergarten and we decided that every Friday I eat lunch with her. I have been to two lunch days with her but for some reason today I completely forgot that lunch was at 10:55 and I left my house at 11:55. I have no idea how I did that, I guess my brain is scattered this morning. This morning we were talking about what she wanted me to bring her and we have been talking about it basically all week. Well I didn’t show and all I can think of is that she was sitting there waiting for me to walk through the doors. Every other kid probably had their parent and I just cried because I know that her little heart is sad for the rest of the day, she probably thinks that I forgot about her. How can I make this up to her and stop beating myself up over this mistake? I know it sounds dramatic, but I really care about her feelings.