Hopefully if you contact Paypal or your bank and explain what happened, they may be able to do something for you.
I know its already been said countless times before, but please, please don't use Paypal F&F to buy anything on here unless they ARE your friend or family and you know its them. Insist on normal goods/services paypal, and if the fee is an issue for the seller, offer to pay the extra 3% to cover it (and yourself). If they still don't agree to use it, and cash on collection isn't an option, run a mile.
Thanks to those who reported the threads and alerted the team, we acted as quickly as we could. An event like this is VERY rare on Basschat but everyone needs to remain vigilant, especially when it comes to sending money to people you don't know in an insecure way. And yeah, if it's too good to be true, it probably isn't.