Transfer Of Najaasat

I utilised the toilet at my parents’ house. I noticed 3 small stains of stool on my underwear (roughly size of a coin). Whilst in the toilet, I vigorously washed the affected area the best I could and then wore the soaking wet underwear. The smell was removed but vague stains remained.

I then sat on the sofa at my parents’ house. As my underwear was considerably wet, the wetness came through my trousers and kurta and some moisture passed on to the sofa.

The sofa is dark in colour so it’s difficult to know if any napaaki went on to it. My logic tells me that it is unlikely that napaaki got on to the sofa. There is no smell of napaaki on the sofa.

Is the sofa paak or do I have to undertake the difficult task of telling my parents to wash it?