All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Merely dropping a pad stained with menstrual blood in the place you mentioned does not necessitate that the impurity transferred to it. Certainty dictates that purity is maintained and that the impurity did not transfer, so use this as the basis and do not consider that the impurity transferred elsewhere unless you have certainty by which you could swear that it actually did.
Therefore, do not be concerned by these whispers (of the Devil) and do not pay attention to them. Instead, turn away from them and use whatever you want to use of your property without worry and without fear.
For more benefit, please refer to Fataawa 91381 and 87127.
Allaah Knows best.