It's a scam. There is no explanation or proof as to why your order never arrives and you are still being charged.
Read from their website: Please Note: If your order is returned to us due to a banned/restricted products policy, a wrong address, refusal to pay customs fees, refusal to accept the order or because no one was there to accept delivery of your order, we will refund your credit card as follows: You will be refunded the total amount of the order, minus the shipping charge, and 20% of the value of the order, (as a re-stocking fee). We will also subtract any other outside charges iHerb.com has incurred during shipping, such as warehousing fees, return postage fees, etc.
There is NO proof that the product was ever shipped. They are making money based on this claim. Charging you for the order and then credit return you -20% and shipping.