.. How to find the toothbrush

The toothbrush is of course next to the washbasin on the 2nd floor. That's it, onwards!

Did you get it? Maybe you could trap it with something.

Like, a mouse trap. The closets are full of mice.

There is a closet in the bottom floor. Try there.

You need some kind of device to open the closet. Like an impromptu handle!

One way to attach a handle to a door would be using suction.

Maybe there is a plunger somewhere in the house.

In the toilet. Open the bathroom door and take the plunger. Use it on the closet door.

The mouse trap? Inside the closet. Go on, don't be scared.

You can use the mouse trap to catch that cocky toothbrush! You just need a bait. Go through your stuff.

Yeah, bait to catch the toothbrush with the mouse trap.
Maybe you could sacrifice one of your precious provisions for a good cause.

Combine the provisions with the mouse trap and use the combined wasabi-trap on the dark corner between the 1st and 2nd floor stairs.