This is an ABSOLUTELY CLASSIC Craigslist fraud, to common that Craigslist has gone to exceptional lengths to warn sellers. The scammers offer deals far to good to be true, but too attractive to buyers to heed the warnings. The law is clear that the funds don't belong to the seller upon deposit, but upon collection-- which takes as much at ten days. When the seller sends good money to the scammer, the seller must cover that payment.
Sorry to have to bring you bad news, but liability is not in the bank, it is yours.
Best wishes for an outcome you can accept, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.