If your son finds a tiny baby rabbit in the yard while mowing, your husband will let him bring it inside rather than leaving it alone.
Once inside the house baby bunny is so cute and little and likes snuggling up with your puppy so you let the kids put it in a box filled with soft cloths and tell them they can put it back outside in the morning.
Once inside the box the bunny looks so little that your son does not think he needs to take precautions like putting a lid on the box and closing his bedroom door.
Since the lid is not on the box and the bedroom door is not closed, when you wake up in the morning and look into the box, you find it empty except for all those soft cloths.
Since the cloths are all that is in the box and the bedroom door is open and you have absolutely no idea how long said bunny has been wandering in the house, you have no idea where to even begin looking.
Since you have no idea where to start looking, you figure upstairs would be the likeliest choice so you grab a flashlight and begin tearing apart each upstairs bedroom looking under every piece of furniture and moving every item on the floor.
Because the baby bunny is nowhere to be found upstairs, you take you flashlight downstairs and start moving things around and looking under furniture there.
Looking under furniture, you just might find a tiny little bunny in the music/school room cuddled against a stuffed animal that was stuffed in a corner under a bookshelf.
Once you find the bunny and because it is still early in the morning, you send your son outside with the bunny and release it back into the wild where it belongs.