Regardless of whether or not your housemate is a cunt (which I'm guessing you think they are if you've made a thread about it), that's less than an hour's work to sort out. Making a big deal about will surely make your home life awkward and unpleasant. If it were me, I'd tidy up very angrily (but quite quietly) and then ask them not to do it again, for the sake of an easier life in the long run.
Regardless of whether or not your housemate is a cunt (which I'm guessing you think they are if you've made a thread about it), that's less than an hour's work to sort out. Making a big deal about will surely make your home life awkward and unpleasant. If it were me, I'd tidy up very angrily (but quite quietly) and then ask them not to do it again, for the sake of an easier life in the long run.