Had to go somewhere,Something happened in the family,did it but brother/sister/cousin played with it 或者 drew on it because they thought it was scratch paper,mom saw it on the floor thought it was trash and threw it away,cleaning up the house and threw it,spilled something on it,flew out the window (say your 台, 办公桌 is near an open window,)sister/brother/cousin teared it 或者 threw to it to the ground because 你 didnt do want he/she wanted 你 to do... Think.