Is there anything in Norco (hydrocodone and acetaminophen) or anything about hepatitis C or liver damages that can cause false cocaine results in a mouth swab test?

Not that I know of. Norco (hydrocodone and acetaminophen) is a combination of acetaminophen (which you should be very cautious with if you have hep C) and hydrocodone, and am unaware of any false positives with either drug, or with hep C. Any positive on either a urine or saliva test should be subjected to confirmation, which can tell a false positive from a true one.