Assalamualaikum. A person live in a house that one member of the family did not clean the impure correctly. There is still the najasah in the floor even though she think she has clean it. When he advice her that what was her doing is wrong, she would not listen. So when the other family members walk on top of the najasah, najasah move to every place without peoples realizing. One person in the family realizing that but could not know where the najasah has move to in the house. What is the law on that situation for prayer and did the najasah is forgiven?
In principle, if one had stepped on an impure floor which is wet and moist then the feet has become impure. If the impure floor was dry and the feet was wet then the feet wont become impure if the floor has not become wet due to it. However, if the floor becomes wet to such an extent that the wetness of it can also transmit to other places i.e. if you was to place another cloth or rug on top of it, then the feet has become impure.
So in the scenario above, the places will not be impure if there are no traces of impurity of smell and colour.
The method of cleaning the carpet or rug pour water over it three times and with every wash let the drops of water cease, if it is hard to rinse. If it is not then it should be rinsed. Alternatively, you can just use wet cloth and wipe few times until you are satisfied that it’s clean. Also, Salah on it is allowed.