Lock it in a cage with a dog?

I think you would have to do a DNA test. That is what they did in this article: http://www.messybeast.com/small-hybrids/rufus-lynx-hybrids.htm

The likelihood that your cat has any bobcat/lynx blood in it, is almost none. Wild cat/domestic cat crosses, when they succeed at all, do not produce animals with domestic temperament. Another major problem with wild/domestic cat crosses, never mentioned by people who are tryiing to promote cats claimed to have wild blood in them, is that cats who are genuinely hybrids of wildcat x domestic cat, at least in the early generations after the initial cross, have one unpleasant characteristic of the wild ancestry. If you think the odor of an intact tomcat's urine smells bad, its nothing compared to the powerful odor of wildcat urine! Wildcat x domestic cat crosses at least in early generations, have much stronger smelling urine than their domestic ancestors, a trait that few people would appreciate in a housepet! This site addresses the topic of wild x domestic cat hybrids very well. It also points out that: The idea of a bobcat hybrid that would combine the looks and best traits of a bobcat while using a domestic to reduce the behavior problems has a lot of appeal. Although there have been claims of bobcats mating with domestics for centuries, those claims have never been proven in a way that convinces anyone with a scientific background. However, that hasn’t stopped breeders from creating legends and offering bobcat hybrids for sale http://www.exoticcatz.com/sphybridsbobcat.html With the availability of DNA technology that could positively prove that a cat was a bobcat x domestic cat cross, if it really was, don't you think that people who claim to be breeding such hybrids would be eager to prove their claims with DNA testing? Proof via DNA would certainly validate that their breeds are genuinely as they claim them to be! Yet nobody has dared take the step of having their claims validated by DNA test results! This article expertly addresses some of the issues that arise when attempting to succeed in creating wildcat x domestic cat hybrids. http://www.messybeast.com/small-hybrids/fertility-hybrids.htm To compare truth vs fiction, compare the hype on the Pixiebobs, to the history of a breed that is genuinely descended from a wildcat x domestic cat hybridization. http://www.bengalcat.me.uk/The%20history%20of%20the%20Bengal%20cat.htm Note that the Bengal cat history provides detailed information, including naming authoritative sources that can validate and prove that this breed was created from domestic x wildcat hybridization. Note also that there is documentation and records kept to validate the first cross between the wildcats and the domestic cats used to create the breed. Compare the Bengal's history and verifiable facts to the vague hyped assumptions made about the cats claimed to have originated the Pixiebob breed. There's definitely no definite witnessing of breeding between the bobcat and domestic cats, no documentation, nothing that can be verified or proven (unexcusable when DNA testing could easily prove the claim if it was true!) http://www.messybeast.com/small-hybrids/hybrids.htm This list is excellent, showing which claimed domestic x wild cat hybrids have been claimed and those which have been proven and validated as real.