You were 本來 originally going to go grab the 本 notebook from the bookshelf, but it spontaneously floated off and 來 came to you! You 本來 originally had no idea your 本 notebook could 來 come to you like this. Now you know.
Usage
本來 的 意思
original meaning
她 本來 明年 想 去 台灣。
She originally was thinking to go to Taiwan next year.