I was surprised to realise I had forgotten my lesson notes.
「レッスンノートがなくて とてもショックでした」= I was shocked that there were no lesson notes. / I was shocked to find there were no lesson notes. / I was surprised to realise I had forgotten my lesson notes.
「レッスンノートがない」理由によって違う英語になります。先生が用意していない時にこちらの文章を使います:
I was shocked that there were no lesson notes.
I was shocked that the teacher had not prepared lesson notes.
自分が「レッスンノート」を忘れた場合にはこちらの英語を使えます。
I was shocked to find I had forgotten my lesson notes.
I was surprised to realise that I hadn't brought my lesson notes.