In Los Angeles pawnshops are heavily regulated. The vice and robbery divisions check their paperwork regularly...at least that was the policy when my cousin had his shop in Venice for over 20 years.

The police would let him know when traceable items had been stolen. He would notify them if he thought an item was hinky. He had such a good relationship with the police, that when he had a heart attack, during his recuperation off-duty officers would help his wife keep the business going.

That said, are all pawn brokers scrupulous? Probably not, but most are or they don't stay in business.