The facebook group owners might be referring to the bad buyer/trader/seller group on fb maybe.
From the info you provide below if you have paid for the item (weeks ago) it seems only right that it should be shipped (and it shouldn't be that much trouble for the seller to give you the shipping info, surely?).
If you're seeking advice on how to handle this situation try posting (or asking for this thread to be moved) to trader & classified support here on the arena. You'll see it in the navigation menu