[il] Bf Posted A Fire Chiefs Badge For Sale On Facebook, Police Dept Shows Up Demanding He Give It Back As

My boyfriend purchased a fire chiefs badge for a neighboring city at an estate sale roughly two years ago. He put it on facebook marketplace to sell it to get some extra cash. Now, the police and fire dept from the neighboring city contacted us and said that it was stolen and they want it back. They went as far as showing up on our doorstep to demand it back (they are in a different city and county, so they don’t have jurisdiction here). The badge has no serial numbers or badge number — so there’s no way to identify the badge outside of the name of the city and that it says fire chief on it. We told them that we wanted to contact a lawyer and see what our options were, because we paid a lot of money for this item and don’t want to lose the money we invested in buying it. We don’t even know how they got our address. We don’t use our full name on Facebook. We think they used another profile and posed as an interested buyer who my bf gave the address to and then they just showed up here with four or five officers. This is all happening in Illinois. And the badge is a vintage badge, probably from the seventies. Any advice would be appreciated.