Most states do keep a database of insurance policies in force on a particular VIN. Not just currently, either. Insurance Guy has access to that database and can even see stuff like who has insured that VIN throughout its history–company, policy number, other people residing in that same household, and what other cars are insured and with whom in that household; who is/has been the registered owner of that VIN, where that VIN has been garaged, surely some other info I’m not thinking of right now. Hack that database and you’ve got some useful information. For instance, with just a license plate number, Insurance Guy can identify the registered owner, the address, the insurance history of that car; and then cross reference that data to also identify other cars registered at the same residence, those plates & insurance, as well as the owners’ names, SSNs, DOBs, date of death (when applicable), addresses lived at by those names & SSNs, who else has lived at those addresses in the same time windows…all going back to when the data base was created (I’ve looked back as far as the late 90s I believe). Oh, and you can also tap into claim history. There are a handful of states that don’t feed the database, but I couldn’t tell you which ones.
In addition to the weird Craigslist style scams, this could also be something more simple: someone wants to pin their car’s collision damage on someone else. I saw this from time to time as an adjuster. Scammer reports the claim, and badgers the adjuster to make a decision to inspect and pay for the damage. Protocol is for the adjuster to contact the insured first, but sometimes the insured doesn’t return calls because, “WTF? My car wasn’t in an accident, that must be a scammer posing as my insurance company.” Meanwhile, scammer is really getting nasty with the adjuster (who is criminally overworked and underthanked anyway). Harassing calls & emails, multiple times a day, very foul stuff sometimes, bonus points if scammer has a really thick accent but refuses an interpreter because “Me English much good, no need translator! Just fix car you big stupid!” Some adjusters can’t handle it and just reason: “Well, my insured isn’t calling back. Surely they would if someone were falsely accusing them. This one must be legit.” And then they go ahead and pay the claim.