It may be too little, too late now, but did you have an option originally of taking a credit instead of pushing for a refund of what little taxes and fees there were? A $5000 voucher sounds much more worthwhile than a $270 refund....

Unfortunately, it seems that the tax refund has already been credited to your account. I don't believe you are "entitled" to anything else. It may be worth writing nicely to LH customer service to see if they might issue you a goodwill voucher to offset some of the 4.7k loss