It's very common with bikes, it wouldn't surprise me if they do it with cars too. I found my own stolen bike for sale on Facebook but still wasn't able to recover it. They just use a stolen or anonymized Facebook account so you can't easily figure out who is selling it.

I once saw a story about someone who saw her bike on sale even before it was stolen. The thieves announce the bikes they see regularly in the same place in the street and only steal them if they have a potential buyer.

That way they only take the risk when they need to, they don't need any storage area, and if they are caught it is only for 1 bike, not tens or hundreds.

When you or a friend show up to a public place to buy it, it’s usually pretty clear who’s selling it.