Scatterbrain

I went to a birthday party on Saturday and on my way there, I realized that I left the present back at my apartment. So I learned a new word, the sound of which I love so much I can't stand it: OCCHOKOCHOI

おっちょこちょい (adj-na,n) careless person; scatterbrain; birdbrain

This one will also work:

そそっかしい (adj-i) careless; thoughtless

I wonder whether it's related to this one:

そそくさ (adv-to) (on-mim) hurriedly; in haste