In the 2000s Craigslist was threatened by a coalition of 40 state attorneys general into policing their sex ads....Facebook will need something similar.
Facebook has all the information any willing police officer/DA would need to capture the thieves. All they would need to do is go to a judge and ask.
Also the legislature could make laws to make it easier to send bike thieves to jail.
The government != Facebook and it's better that way since we can vote to change things that we find wrong with the government, but lack that ability with FB
Traditional retailers of used goods like pawn shops are usually subject to pretty stringent regulation - not necessarily to determine if goods are stolen, but to record identification of the seller to enable an investigation later. In some places this does include proactively sending a report of items to the police for checking against stolen reports. So there's a pretty clear precedent for regulation of this kind directed towards online marketplaces, but you can no doubt predict the questions around the difference between a pawn shop (being the seller) and Facebook (being not the seller but just a provider of listings).
States enforce pawn laws through electronic systems like LEADS. FB, offerup, and every other platform out there letting thieves fence things with impunity could implement same.