I lived in Indiana and had read cases about this. You can hide your vehicle, however they can come and get it so long as they do it peacefully. If you come out and see your car being towed, just make a huge deal of it and start yelling. That way the court will make their repossession invalid and give you back the car.
Ultimately, you are going to have to give back the car or pay what you owe. It won't last forever. Good luck and I hope this helps!
The statute below is what you were talking about, but as you can see, does not apply to your set of facts.
720 ILCS 5/16-1
(a) A person commits theft when he knowingly:
(1) Obtains or exerts unauthorized control over property of the owner; or
(2) Obtains by deception control over property of the owner; or
(3) Obtains by threat control over property of the owner; or
(4) Obtains control over stolen property knowing the property to have been stolen or under such circumstances as would reasonably induce him to believe that the property was stolen; or
(5) Obtains or exerts control over property in the custody of any law enforcement agency which is explicitly represented to him by any law enforcement officer or any individual acting in behalf of a law enforcement agency as being stolen, and
(A) Intends to deprive the owner permanently of the use or benefit of the property; or
(B) Knowingly uses, conceals or abandons the property in such manner as to deprive the owner permanently of such use or benefit; or
(C) Uses, conceals, or abandons the property knowing such use, concealment or abandonment probably will deprive the owner permanently of such use or benefit.