Salem

I had left my character inside a house overnight with full humours, but when i woke up this morning i had apparently been knocked out... is there a way to find out what and by how?

Have you been a bad boy (committing crimes) ?

If so I would assume someone probably summoned you and KOd you

See if you have any scents in your house or on your claim

No, not been doing crimes, and no scents either. and the claim is walled and gated as well.
Is there a log file i could check?

There's no way to find this specific information out other than through old fashion detective work. The only thing you can do is look for evidence of a crime and track down the perpetrator.

Is your house in darkness with no church nearby? That would KO you overnight.