In negative sentences it means "nothing", but what does it mean in positive ones? I found it in this sentence from a song(立ち入り禁止 by まふまふ) and I was wondering what it meant here.
From the context, I feel this 何一つ probably means "(threw away) everything", but the last verse containing this sentence looks a bit like a word salad to me. (Is this even a question? What does she want to know by saying 教えて?) This normally has to be 何もかも if "everything" is intended. Maybe this is a simulation of the half-broken mentality of the speaker, so it may not be supposed to make sense as a perfect Japanese sentence.