Does the bed on which a ritually impure person (junub) slept become impure if there is no trace of ritual impurity on it, given that the impure person, his outer clothes, and his hands are stained with it?

If a person in a state of ritual impurity (junub) sleeps on a bed, and semen has reached the bed, the preponderant opinion is that semen is pure, so this does not affect the purity of the bed. However, if there was another impurity, such as madhi (pre-seminal fluid), and its transfer to the bed is not known, the original state of the bed's purity remains; because the transfer of impurity is not ruled by mere doubt, so there is no need for worry or doubt.