Ghost? wrote with my son's blocks on floor!! it is not a lie, please help me understand! i never believed!?

Taking my 2 yrs old back to hiss room to put his pjs on, I (working inm medical field, totally cold headed, pretty grounded, never believe in stuff like that) blocks put very neatly on his floor that said help me. The block bag is opened n the side, only those blocks are out. I freak out call my husband getting pretty upset at him thinking he did it but when he starts telling me he dudnt that he was not even there...my son by then has thrown the rest of the blocks on the floor to play so when my hbby comes too late and barely believed me. Now I am truly scared don't understand, why me? I am such a chicken! What do I do? I couldn't keep my son in his room..