That is a great question.

I can speculate on a few things:

* Pawn shop owners let police peruse their transaction lists whenever asks. Perhaps similar to how cops may look past low level crimes in order to make bigger cases.

* Perhaps akin to police being able to affect traffic stops in areas with high crime, and/or high incidents of DUI's, the police are allowed to look at records as Pawnshops were a known vector for stolen property.

* The police were investigating theft, where a stolen item showed up in a pawn-shop, and were lawfully reviewing the transaction records.