IMO there is no way the owner of the Gano house could know if something there happened or not just by lack of blood.
If Somer was strangled for instance, no one could tell by looking at the house.
IMO even if there were blood, it was possibly not visable after LE released the house.
The only way he/she would know, is if LE told her/him. But, since LE is being so tight lipped, I don't think they would give details of the house. They would just release it after their investigation was wrapped up.
I think the owner just does not want to think it happened there or does not want the house to be known as the house Somer was killed in.
This is JMO