Harbor Freight Tools Did not inform me of restock fee prior to purchase Memphis Tennessee

I purchased a general purpose 12v pump to transfer fuel on 07/10/14.  I returned the pump because it cant be used with fuel on 07/15/14. This was not stated on the box the pump came in, but was on sticker label on pump. The cashier who was doing my refund informed me that there was a 20% restocking fee. I asked why. I was told I was informed prior to purchase that the pump qualified for this restock fee. No one told me at the register prior to purchase nor are there signs posted in store of this policy. I was told the policy is printed on the receipt. That does me no good after I had already purchased the pump. Harbor Freight tools should post in store in plain view the restock fee policy so buyer can know before they purchase any product that has a restock fee. I will not do business with this retailer anymore.