Even if you didn't know it was stolen you are still going for the ride and you are gonna loose your gun, plain and simple. Receiving stolen property means just what it says. Don't know about anyone else but when and if I buy anything from someone I am getting a receipt and in the case of any gun I am getting it checked. There are TONS of stolen guns out there guys. Tons of them.
IC 35-43-4-2
Theft; receiving stolen property
(b) A person who knowingly or intentionally receives, retains, or disposes of the property of another person that has been the subject of theft commits receiving stolen property, a Class D felony.
Only if the police have probable cause that the person knows the property is stolen would they be arrested. At least, in a jurisdiction with honest police officers who know and follow the law.